Import Clang, at r72732.vendor/clang/clang-r72732

1 files changed, 4485 insertions, 0 deletions

diff --git a/lib/Sema/SemaOverload.cpp b/lib/Sema/SemaOverload.cpp
new file mode 100644
index 000000000000..98ee13af856a
--- /dev/null
+++ b/lib/Sema/SemaOverload.cpp
@@ -0,0 +1,4485 @@
+//===--- SemaOverload.cpp - C++ Overloading ---------------------*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file provides Sema routines for C++ overloading.
+//
+//===----------------------------------------------------------------------===//
+
+#include "Sema.h"
+#include "SemaInherit.h"
+#include "clang/Basic/Diagnostic.h"
+#include "clang/Lex/Preprocessor.h"
+#include "clang/AST/ASTContext.h"
+#include "clang/AST/Expr.h"
+#include "clang/AST/ExprCXX.h"
+#include "clang/AST/TypeOrdering.h"
+#include "llvm/ADT/SmallPtrSet.h"
+#include "llvm/ADT/STLExtras.h"
+#include "llvm/Support/Compiler.h"
+#include <algorithm>
+
+namespace clang {
+
+/// GetConversionCategory - Retrieve the implicit conversion
+/// category corresponding to the given implicit conversion kind.
+ImplicitConversionCategory 
+GetConversionCategory(ImplicitConversionKind Kind) {
+  static const ImplicitConversionCategory
+    Category[(int)ICK_Num_Conversion_Kinds] = {
+    ICC_Identity,
+    ICC_Lvalue_Transformation,
+    ICC_Lvalue_Transformation,
+    ICC_Lvalue_Transformation,
+    ICC_Qualification_Adjustment,
+    ICC_Promotion,
+    ICC_Promotion,
+    ICC_Promotion,
+    ICC_Conversion,
+    ICC_Conversion,
+    ICC_Conversion,
+    ICC_Conversion,
+    ICC_Conversion,
+    ICC_Conversion,
+    ICC_Conversion,
+    ICC_Conversion,
+    ICC_Conversion,
+    ICC_Conversion
+  };
+  return Category[(int)Kind];
+}
+
+/// GetConversionRank - Retrieve the implicit conversion rank
+/// corresponding to the given implicit conversion kind.
+ImplicitConversionRank GetConversionRank(ImplicitConversionKind Kind) {
+  static const ImplicitConversionRank
+    Rank[(int)ICK_Num_Conversion_Kinds] = {
+    ICR_Exact_Match,
+    ICR_Exact_Match,
+    ICR_Exact_Match,
+    ICR_Exact_Match,
+    ICR_Exact_Match,
+    ICR_Promotion,
+    ICR_Promotion,
+    ICR_Promotion,
+    ICR_Conversion,
+    ICR_Conversion,
+    ICR_Conversion,
+    ICR_Conversion,
+    ICR_Conversion,
+    ICR_Conversion,
+    ICR_Conversion,
+    ICR_Conversion,
+    ICR_Conversion,
+    ICR_Conversion
+  };
+  return Rank[(int)Kind];
+}
+
+/// GetImplicitConversionName - Return the name of this kind of
+/// implicit conversion.
+const char* GetImplicitConversionName(ImplicitConversionKind Kind) {
+  static const char* Name[(int)ICK_Num_Conversion_Kinds] = {
+    "No conversion",
+    "Lvalue-to-rvalue",
+    "Array-to-pointer",
+    "Function-to-pointer",
+    "Qualification",
+    "Integral promotion",
+    "Floating point promotion",
+    "Complex promotion",
+    "Integral conversion",
+    "Floating conversion",
+    "Complex conversion",
+    "Floating-integral conversion",
+    "Complex-real conversion",
+    "Pointer conversion",
+    "Pointer-to-member conversion",
+    "Boolean conversion",
+    "Compatible-types conversion",
+    "Derived-to-base conversion"
+  };
+  return Name[Kind];
+}
+
+/// StandardConversionSequence - Set the standard conversion
+/// sequence to the identity conversion.
+void StandardConversionSequence::setAsIdentityConversion() {
+  First = ICK_Identity;
+  Second = ICK_Identity;
+  Third = ICK_Identity;
+  Deprecated = false;
+  ReferenceBinding = false;
+  DirectBinding = false;
+  RRefBinding = false;
+  CopyConstructor = 0;
+}
+
+/// getRank - Retrieve the rank of this standard conversion sequence
+/// (C++ 13.3.3.1.1p3). The rank is the largest rank of each of the
+/// implicit conversions.
+ImplicitConversionRank StandardConversionSequence::getRank() const {
+  ImplicitConversionRank Rank = ICR_Exact_Match;
+  if  (GetConversionRank(First) > Rank)
+    Rank = GetConversionRank(First);
+  if  (GetConversionRank(Second) > Rank)
+    Rank = GetConversionRank(Second);
+  if  (GetConversionRank(Third) > Rank)
+    Rank = GetConversionRank(Third);
+  return Rank;
+}
+
+/// isPointerConversionToBool - Determines whether this conversion is
+/// a conversion of a pointer or pointer-to-member to bool. This is
+/// used as part of the ranking of standard conversion sequences 
+/// (C++ 13.3.3.2p4).
+bool StandardConversionSequence::isPointerConversionToBool() const
+{
+  QualType FromType = QualType::getFromOpaquePtr(FromTypePtr);
+  QualType ToType = QualType::getFromOpaquePtr(ToTypePtr);
+
+  // Note that FromType has not necessarily been transformed by the
+  // array-to-pointer or function-to-pointer implicit conversions, so
+  // check for their presence as well as checking whether FromType is
+  // a pointer.
+  if (ToType->isBooleanType() &&
+      (FromType->isPointerType() || FromType->isBlockPointerType() ||
+       First == ICK_Array_To_Pointer || First == ICK_Function_To_Pointer))
+    return true;
+
+  return false;
+}
+
+/// isPointerConversionToVoidPointer - Determines whether this
+/// conversion is a conversion of a pointer to a void pointer. This is
+/// used as part of the ranking of standard conversion sequences (C++
+/// 13.3.3.2p4).
+bool 
+StandardConversionSequence::
+isPointerConversionToVoidPointer(ASTContext& Context) const
+{
+  QualType FromType = QualType::getFromOpaquePtr(FromTypePtr);
+  QualType ToType = QualType::getFromOpaquePtr(ToTypePtr);
+
+  // Note that FromType has not necessarily been transformed by the
+  // array-to-pointer implicit conversion, so check for its presence
+  // and redo the conversion to get a pointer.
+  if (First == ICK_Array_To_Pointer)
+    FromType = Context.getArrayDecayedType(FromType);
+
+  if (Second == ICK_Pointer_Conversion)
+    if (const PointerType* ToPtrType = ToType->getAsPointerType())
+      return ToPtrType->getPointeeType()->isVoidType();
+
+  return false;
+}
+
+/// DebugPrint - Print this standard conversion sequence to standard
+/// error. Useful for debugging overloading issues.
+void StandardConversionSequence::DebugPrint() const {
+  bool PrintedSomething = false;
+  if (First != ICK_Identity) {
+    fprintf(stderr, "%s", GetImplicitConversionName(First));
+    PrintedSomething = true;
+  }
+
+  if (Second != ICK_Identity) {
+    if (PrintedSomething) {
+      fprintf(stderr, " -> ");
+    }
+    fprintf(stderr, "%s", GetImplicitConversionName(Second));
+
+    if (CopyConstructor) {
+      fprintf(stderr, " (by copy constructor)");
+    } else if (DirectBinding) {
+      fprintf(stderr, " (direct reference binding)");
+    } else if (ReferenceBinding) {
+      fprintf(stderr, " (reference binding)");
+    }
+    PrintedSomething = true;
+  }
+
+  if (Third != ICK_Identity) {
+    if (PrintedSomething) {
+      fprintf(stderr, " -> ");
+    }
+    fprintf(stderr, "%s", GetImplicitConversionName(Third));
+    PrintedSomething = true;
+  }
+
+  if (!PrintedSomething) {
+    fprintf(stderr, "No conversions required");
+  }
+}
+
+/// DebugPrint - Print this user-defined conversion sequence to standard
+/// error. Useful for debugging overloading issues.
+void UserDefinedConversionSequence::DebugPrint() const {
+  if (Before.First || Before.Second || Before.Third) {
+    Before.DebugPrint();
+    fprintf(stderr, " -> ");
+  }
+  fprintf(stderr, "'%s'", ConversionFunction->getNameAsString().c_str());
+  if (After.First || After.Second || After.Third) {
+    fprintf(stderr, " -> ");
+    After.DebugPrint();
+  }
+}
+
+/// DebugPrint - Print this implicit conversion sequence to standard
+/// error. Useful for debugging overloading issues.
+void ImplicitConversionSequence::DebugPrint() const {
+  switch (ConversionKind) {
+  case StandardConversion:
+    fprintf(stderr, "Standard conversion: ");
+    Standard.DebugPrint();
+    break;
+  case UserDefinedConversion:
+    fprintf(stderr, "User-defined conversion: ");
+    UserDefined.DebugPrint();
+    break;
+  case EllipsisConversion:
+    fprintf(stderr, "Ellipsis conversion");
+    break;
+  case BadConversion:
+    fprintf(stderr, "Bad conversion");
+    break;
+  }
+
+  fprintf(stderr, "\n");
+}
+
+// IsOverload - Determine whether the given New declaration is an
+// overload of the Old declaration. This routine returns false if New
+// and Old cannot be overloaded, e.g., if they are functions with the
+// same signature (C++ 1.3.10) or if the Old declaration isn't a
+// function (or overload set). When it does return false and Old is an
+// OverloadedFunctionDecl, MatchedDecl will be set to point to the
+// FunctionDecl that New cannot be overloaded with. 
+//
+// Example: Given the following input:
+//
+//   void f(int, float); // #1
+//   void f(int, int); // #2
+//   int f(int, int); // #3
+//
+// When we process #1, there is no previous declaration of "f",
+// so IsOverload will not be used. 
+//
+// When we process #2, Old is a FunctionDecl for #1.  By comparing the
+// parameter types, we see that #1 and #2 are overloaded (since they
+// have different signatures), so this routine returns false;
+// MatchedDecl is unchanged.
+//
+// When we process #3, Old is an OverloadedFunctionDecl containing #1
+// and #2. We compare the signatures of #3 to #1 (they're overloaded,
+// so we do nothing) and then #3 to #2. Since the signatures of #3 and
+// #2 are identical (return types of functions are not part of the
+// signature), IsOverload returns false and MatchedDecl will be set to
+// point to the FunctionDecl for #2.
+bool
+Sema::IsOverload(FunctionDecl *New, Decl* OldD, 
+                 OverloadedFunctionDecl::function_iterator& MatchedDecl)
+{
+  if (OverloadedFunctionDecl* Ovl = dyn_cast<OverloadedFunctionDecl>(OldD)) {
+    // Is this new function an overload of every function in the
+    // overload set?
+    OverloadedFunctionDecl::function_iterator Func = Ovl->function_begin(),
+                                           FuncEnd = Ovl->function_end();
+    for (; Func != FuncEnd; ++Func) {
+      if (!IsOverload(New, *Func, MatchedDecl)) {
+        MatchedDecl = Func;
+        return false;
+      }
+    }
+
+    // This function overloads every function in the overload set.
+    return true;
+  } else if (FunctionDecl* Old = dyn_cast<FunctionDecl>(OldD)) {
+    // Is the function New an overload of the function Old?
+    QualType OldQType = Context.getCanonicalType(Old->getType());
+    QualType NewQType = Context.getCanonicalType(New->getType());
+
+    // Compare the signatures (C++ 1.3.10) of the two functions to
+    // determine whether they are overloads. If we find any mismatch
+    // in the signature, they are overloads.
+
+    // If either of these functions is a K&R-style function (no
+    // prototype), then we consider them to have matching signatures.
+    if (isa<FunctionNoProtoType>(OldQType.getTypePtr()) ||
+        isa<FunctionNoProtoType>(NewQType.getTypePtr()))
+      return false;
+
+    FunctionProtoType* OldType = cast<FunctionProtoType>(OldQType.getTypePtr());
+    FunctionProtoType* NewType = cast<FunctionProtoType>(NewQType.getTypePtr());
+
+    // The signature of a function includes the types of its
+    // parameters (C++ 1.3.10), which includes the presence or absence
+    // of the ellipsis; see C++ DR 357).
+    if (OldQType != NewQType &&
+        (OldType->getNumArgs() != NewType->getNumArgs() ||
+         OldType->isVariadic() != NewType->isVariadic() ||
+         !std::equal(OldType->arg_type_begin(), OldType->arg_type_end(),
+                     NewType->arg_type_begin())))
+      return true;
+
+    // If the function is a class member, its signature includes the
+    // cv-qualifiers (if any) on the function itself.
+    //
+    // As part of this, also check whether one of the member functions
+    // is static, in which case they are not overloads (C++
+    // 13.1p2). While not part of the definition of the signature,
+    // this check is important to determine whether these functions
+    // can be overloaded.
+    CXXMethodDecl* OldMethod = dyn_cast<CXXMethodDecl>(Old);
+    CXXMethodDecl* NewMethod = dyn_cast<CXXMethodDecl>(New);
+    if (OldMethod && NewMethod && 
+        !OldMethod->isStatic() && !NewMethod->isStatic() &&
+        OldMethod->getTypeQualifiers() != NewMethod->getTypeQualifiers())
+      return true;
+
+    // The signatures match; this is not an overload.
+    return false;
+  } else {
+    // (C++ 13p1):
+    //   Only function declarations can be overloaded; object and type
+    //   declarations cannot be overloaded.
+    return false;
+  }
+}
+
+/// TryImplicitConversion - Attempt to perform an implicit conversion
+/// from the given expression (Expr) to the given type (ToType). This
+/// function returns an implicit conversion sequence that can be used
+/// to perform the initialization. Given
+///
+///   void f(float f);
+///   void g(int i) { f(i); }
+///
+/// this routine would produce an implicit conversion sequence to
+/// describe the initialization of f from i, which will be a standard
+/// conversion sequence containing an lvalue-to-rvalue conversion (C++
+/// 4.1) followed by a floating-integral conversion (C++ 4.9).
+//
+/// Note that this routine only determines how the conversion can be
+/// performed; it does not actually perform the conversion. As such,
+/// it will not produce any diagnostics if no conversion is available,
+/// but will instead return an implicit conversion sequence of kind
+/// "BadConversion".
+///
+/// If @p SuppressUserConversions, then user-defined conversions are
+/// not permitted.
+/// If @p AllowExplicit, then explicit user-defined conversions are
+/// permitted.
+/// If @p ForceRValue, then overloading is performed as if From was an rvalue,
+/// no matter its actual lvalueness.
+ImplicitConversionSequence
+Sema::TryImplicitConversion(Expr* From, QualType ToType,
+                            bool SuppressUserConversions,
+                            bool AllowExplicit, bool ForceRValue)
+{
+  ImplicitConversionSequence ICS;
+  if (IsStandardConversion(From, ToType, ICS.Standard))
+    ICS.ConversionKind = ImplicitConversionSequence::StandardConversion;
+  else if (getLangOptions().CPlusPlus &&
+           IsUserDefinedConversion(From, ToType, ICS.UserDefined, 
+                                   !SuppressUserConversions, AllowExplicit,
+                                   ForceRValue)) {
+    ICS.ConversionKind = ImplicitConversionSequence::UserDefinedConversion;
+    // C++ [over.ics.user]p4:
+    //   A conversion of an expression of class type to the same class
+    //   type is given Exact Match rank, and a conversion of an
+    //   expression of class type to a base class of that type is
+    //   given Conversion rank, in spite of the fact that a copy
+    //   constructor (i.e., a user-defined conversion function) is
+    //   called for those cases.
+    if (CXXConstructorDecl *Constructor 
+          = dyn_cast<CXXConstructorDecl>(ICS.UserDefined.ConversionFunction)) {
+      QualType FromCanon 
+        = Context.getCanonicalType(From->getType().getUnqualifiedType());
+      QualType ToCanon = Context.getCanonicalType(ToType).getUnqualifiedType();
+      if (FromCanon == ToCanon || IsDerivedFrom(FromCanon, ToCanon)) {
+        // Turn this into a "standard" conversion sequence, so that it
+        // gets ranked with standard conversion sequences.
+        ICS.ConversionKind = ImplicitConversionSequence::StandardConversion;
+        ICS.Standard.setAsIdentityConversion();
+        ICS.Standard.FromTypePtr = From->getType().getAsOpaquePtr();
+        ICS.Standard.ToTypePtr = ToType.getAsOpaquePtr();
+        ICS.Standard.CopyConstructor = Constructor;
+        if (ToCanon != FromCanon)
+          ICS.Standard.Second = ICK_Derived_To_Base;
+      }
+    }
+
+    // C++ [over.best.ics]p4:
+    //   However, when considering the argument of a user-defined
+    //   conversion function that is a candidate by 13.3.1.3 when
+    //   invoked for the copying of the temporary in the second step
+    //   of a class copy-initialization, or by 13.3.1.4, 13.3.1.5, or
+    //   13.3.1.6 in all cases, only standard conversion sequences and
+    //   ellipsis conversion sequences are allowed.
+    if (SuppressUserConversions &&
+        ICS.ConversionKind == ImplicitConversionSequence::UserDefinedConversion)
+      ICS.ConversionKind = ImplicitConversionSequence::BadConversion;
+  } else
+    ICS.ConversionKind = ImplicitConversionSequence::BadConversion;
+
+  return ICS;
+}
+
+/// IsStandardConversion - Determines whether there is a standard
+/// conversion sequence (C++ [conv], C++ [over.ics.scs]) from the
+/// expression From to the type ToType. Standard conversion sequences
+/// only consider non-class types; for conversions that involve class
+/// types, use TryImplicitConversion. If a conversion exists, SCS will
+/// contain the standard conversion sequence required to perform this
+/// conversion and this routine will return true. Otherwise, this
+/// routine will return false and the value of SCS is unspecified.
+bool 
+Sema::IsStandardConversion(Expr* From, QualType ToType, 
+                           StandardConversionSequence &SCS)
+{
+  QualType FromType = From->getType();
+
+  // Standard conversions (C++ [conv])
+  SCS.setAsIdentityConversion();
+  SCS.Deprecated = false;
+  SCS.IncompatibleObjC = false;
+  SCS.FromTypePtr = FromType.getAsOpaquePtr();
+  SCS.CopyConstructor = 0;
+
+  // There are no standard conversions for class types in C++, so
+  // abort early. When overloading in C, however, we do permit 
+  if (FromType->isRecordType() || ToType->isRecordType()) {
+    if (getLangOptions().CPlusPlus)
+      return false;
+
+    // When we're overloading in C, we allow, as standard conversions, 
+  }
+
+  // The first conversion can be an lvalue-to-rvalue conversion,
+  // array-to-pointer conversion, or function-to-pointer conversion
+  // (C++ 4p1).
+
+  // Lvalue-to-rvalue conversion (C++ 4.1): 
+  //   An lvalue (3.10) of a non-function, non-array type T can be
+  //   converted to an rvalue.
+  Expr::isLvalueResult argIsLvalue = From->isLvalue(Context);
+  if (argIsLvalue == Expr::LV_Valid && 
+      !FromType->isFunctionType() && !FromType->isArrayType() &&
+      Context.getCanonicalType(FromType) != Context.OverloadTy) {
+    SCS.First = ICK_Lvalue_To_Rvalue;
+
+    // If T is a non-class type, the type of the rvalue is the
+    // cv-unqualified version of T. Otherwise, the type of the rvalue
+    // is T (C++ 4.1p1). C++ can't get here with class types; in C, we
+    // just strip the qualifiers because they don't matter.
+
+    // FIXME: Doesn't see through to qualifiers behind a typedef!
+    FromType = FromType.getUnqualifiedType();
+  }
+  // Array-to-pointer conversion (C++ 4.2)
+  else if (FromType->isArrayType()) {
+    SCS.First = ICK_Array_To_Pointer;
+
+    // An lvalue or rvalue of type "array of N T" or "array of unknown
+    // bound of T" can be converted to an rvalue of type "pointer to
+    // T" (C++ 4.2p1).
+    FromType = Context.getArrayDecayedType(FromType);
+
+    if (IsStringLiteralToNonConstPointerConversion(From, ToType)) {
+      // This conversion is deprecated. (C++ D.4).
+      SCS.Deprecated = true;
+
+      // For the purpose of ranking in overload resolution
+      // (13.3.3.1.1), this conversion is considered an
+      // array-to-pointer conversion followed by a qualification
+      // conversion (4.4). (C++ 4.2p2)
+      SCS.Second = ICK_Identity;
+      SCS.Third = ICK_Qualification;
+      SCS.ToTypePtr = ToType.getAsOpaquePtr();
+      return true;
+    }
+  }
+  // Function-to-pointer conversion (C++ 4.3).
+  else if (FromType->isFunctionType() && argIsLvalue == Expr::LV_Valid) {
+    SCS.First = ICK_Function_To_Pointer;
+
+    // An lvalue of function type T can be converted to an rvalue of
+    // type "pointer to T." The result is a pointer to the
+    // function. (C++ 4.3p1).
+    FromType = Context.getPointerType(FromType);
+  }
+  // Address of overloaded function (C++ [over.over]).
+  else if (FunctionDecl *Fn 
+             = ResolveAddressOfOverloadedFunction(From, ToType, false)) {
+    SCS.First = ICK_Function_To_Pointer;
+
+    // We were able to resolve the address of the overloaded function,
+    // so we can convert to the type of that function.
+    FromType = Fn->getType();
+    if (ToType->isLValueReferenceType())
+      FromType = Context.getLValueReferenceType(FromType);
+    else if (ToType->isRValueReferenceType())
+      FromType = Context.getRValueReferenceType(FromType);
+    else if (ToType->isMemberPointerType()) {
+      // Resolve address only succeeds if both sides are member pointers,
+      // but it doesn't have to be the same class. See DR 247.
+      // Note that this means that the type of &Derived::fn can be
+      // Ret (Base::*)(Args) if the fn overload actually found is from the
+      // base class, even if it was brought into the derived class via a
+      // using declaration. The standard isn't clear on this issue at all.
+      CXXMethodDecl *M = cast<CXXMethodDecl>(Fn);
+      FromType = Context.getMemberPointerType(FromType,
+                    Context.getTypeDeclType(M->getParent()).getTypePtr());
+    } else
+      FromType = Context.getPointerType(FromType);
+  }
+  // We don't require any conversions for the first step.
+  else {
+    SCS.First = ICK_Identity;
+  }
+
+  // The second conversion can be an integral promotion, floating
+  // point promotion, integral conversion, floating point conversion,
+  // floating-integral conversion, pointer conversion,
+  // pointer-to-member conversion, or boolean conversion (C++ 4p1).
+  // For overloading in C, this can also be a "compatible-type"
+  // conversion.
+  bool IncompatibleObjC = false;
+  if (Context.hasSameUnqualifiedType(FromType, ToType)) {
+    // The unqualified versions of the types are the same: there's no
+    // conversion to do.
+    SCS.Second = ICK_Identity;
+  }
+  // Integral promotion (C++ 4.5).  
+  else if (IsIntegralPromotion(From, FromType, ToType)) {
+    SCS.Second = ICK_Integral_Promotion;
+    FromType = ToType.getUnqualifiedType();
+  } 
+  // Floating point promotion (C++ 4.6).
+  else if (IsFloatingPointPromotion(FromType, ToType)) {
+    SCS.Second = ICK_Floating_Promotion;
+    FromType = ToType.getUnqualifiedType();
+  } 
+  // Complex promotion (Clang extension)
+  else if (IsComplexPromotion(FromType, ToType)) {
+    SCS.Second = ICK_Complex_Promotion;
+    FromType = ToType.getUnqualifiedType();
+  }
+  // Integral conversions (C++ 4.7).
+  // FIXME: isIntegralType shouldn't be true for enums in C++.
+  else if ((FromType->isIntegralType() || FromType->isEnumeralType()) &&
+           (ToType->isIntegralType() && !ToType->isEnumeralType())) {
+    SCS.Second = ICK_Integral_Conversion;
+    FromType = ToType.getUnqualifiedType();
+  }
+  // Floating point conversions (C++ 4.8).
+  else if (FromType->isFloatingType() && ToType->isFloatingType()) {
+    SCS.Second = ICK_Floating_Conversion;
+    FromType = ToType.getUnqualifiedType();
+  }
+  // Complex conversions (C99 6.3.1.6)
+  else if (FromType->isComplexType() && ToType->isComplexType()) {
+    SCS.Second = ICK_Complex_Conversion;
+    FromType = ToType.getUnqualifiedType();
+  }
+  // Floating-integral conversions (C++ 4.9).
+  // FIXME: isIntegralType shouldn't be true for enums in C++.
+  else if ((FromType->isFloatingType() &&
+            ToType->isIntegralType() && !ToType->isBooleanType() &&
+                                        !ToType->isEnumeralType()) ||
+           ((FromType->isIntegralType() || FromType->isEnumeralType()) && 
+            ToType->isFloatingType())) {
+    SCS.Second = ICK_Floating_Integral;
+    FromType = ToType.getUnqualifiedType();
+  }
+  // Complex-real conversions (C99 6.3.1.7)
+  else if ((FromType->isComplexType() && ToType->isArithmeticType()) ||
+           (ToType->isComplexType() && FromType->isArithmeticType())) {
+    SCS.Second = ICK_Complex_Real;
+    FromType = ToType.getUnqualifiedType();
+  }
+  // Pointer conversions (C++ 4.10).
+  else if (IsPointerConversion(From, FromType, ToType, FromType, 
+                               IncompatibleObjC)) {
+    SCS.Second = ICK_Pointer_Conversion;
+    SCS.IncompatibleObjC = IncompatibleObjC;
+  }
+  // Pointer to member conversions (4.11).
+  else if (IsMemberPointerConversion(From, FromType, ToType, FromType)) {
+    SCS.Second = ICK_Pointer_Member;
+  }
+  // Boolean conversions (C++ 4.12).
+  else if (ToType->isBooleanType() &&
+           (FromType->isArithmeticType() ||
+            FromType->isEnumeralType() ||
+            FromType->isPointerType() ||
+            FromType->isBlockPointerType() ||
+            FromType->isMemberPointerType() ||
+            FromType->isNullPtrType())) {
+    SCS.Second = ICK_Boolean_Conversion;
+    FromType = Context.BoolTy;
+  }
+  // Compatible conversions (Clang extension for C function overloading)
+  else if (!getLangOptions().CPlusPlus && 
+           Context.typesAreCompatible(ToType, FromType)) {
+    SCS.Second = ICK_Compatible_Conversion;
+  } else {
+    // No second conversion required.
+    SCS.Second = ICK_Identity;
+  }
+
+  QualType CanonFrom;
+  QualType CanonTo;
+  // The third conversion can be a qualification conversion (C++ 4p1).
+  if (IsQualificationConversion(FromType, ToType)) {
+    SCS.Third = ICK_Qualification;
+    FromType = ToType;
+    CanonFrom = Context.getCanonicalType(FromType);
+    CanonTo = Context.getCanonicalType(ToType);
+  } else {
+    // No conversion required
+    SCS.Third = ICK_Identity;
+
+    // C++ [over.best.ics]p6: 
+    //   [...] Any difference in top-level cv-qualification is
+    //   subsumed by the initialization itself and does not constitute
+    //   a conversion. [...]
+    CanonFrom = Context.getCanonicalType(FromType);
+    CanonTo = Context.getCanonicalType(ToType);    
+    if (CanonFrom.getUnqualifiedType() == CanonTo.getUnqualifiedType() &&
+        CanonFrom.getCVRQualifiers() != CanonTo.getCVRQualifiers()) {
+      FromType = ToType;
+      CanonFrom = CanonTo;
+    }
+  }
+
+  // If we have not converted the argument type to the parameter type,
+  // this is a bad conversion sequence.
+  if (CanonFrom != CanonTo)
+    return false;
+
+  SCS.ToTypePtr = FromType.getAsOpaquePtr();
+  return true;
+}
+
+/// IsIntegralPromotion - Determines whether the conversion from the
+/// expression From (whose potentially-adjusted type is FromType) to
+/// ToType is an integral promotion (C++ 4.5). If so, returns true and
+/// sets PromotedType to the promoted type.
+bool Sema::IsIntegralPromotion(Expr *From, QualType FromType, QualType ToType)
+{
+  const BuiltinType *To = ToType->getAsBuiltinType();
+  // All integers are built-in.
+  if (!To) {
+    return false;
+  }
+
+  // An rvalue of type char, signed char, unsigned char, short int, or
+  // unsigned short int can be converted to an rvalue of type int if
+  // int can represent all the values of the source type; otherwise,
+  // the source rvalue can be converted to an rvalue of type unsigned
+  // int (C++ 4.5p1).
+  if (FromType->isPromotableIntegerType() && !FromType->isBooleanType()) {
+    if (// We can promote any signed, promotable integer type to an int
+        (FromType->isSignedIntegerType() ||
+         // We can promote any unsigned integer type whose size is
+         // less than int to an int.
+         (!FromType->isSignedIntegerType() && 
+          Context.getTypeSize(FromType) < Context.getTypeSize(ToType)))) {
+      return To->getKind() == BuiltinType::Int;
+    }
+
+    return To->getKind() == BuiltinType::UInt;
+  }
+
+  // An rvalue of type wchar_t (3.9.1) or an enumeration type (7.2)
+  // can be converted to an rvalue of the first of the following types
+  // that can represent all the values of its underlying type: int,
+  // unsigned int, long, or unsigned long (C++ 4.5p2).
+  if ((FromType->isEnumeralType() || FromType->isWideCharType())
+      && ToType->isIntegerType()) {
+    // Determine whether the type we're converting from is signed or
+    // unsigned.
+    bool FromIsSigned;
+    uint64_t FromSize = Context.getTypeSize(FromType);
+    if (const EnumType *FromEnumType = FromType->getAsEnumType()) {
+      QualType UnderlyingType = FromEnumType->getDecl()->getIntegerType();
+      FromIsSigned = UnderlyingType->isSignedIntegerType();
+    } else {
+      // FIXME: Is wchar_t signed or unsigned? We assume it's signed for now.
+      FromIsSigned = true;
+    }
+
+    // The types we'll try to promote to, in the appropriate
+    // order. Try each of these types.
+    QualType PromoteTypes[6] = { 
+      Context.IntTy, Context.UnsignedIntTy, 
+      Context.LongTy, Context.UnsignedLongTy ,
+      Context.LongLongTy, Context.UnsignedLongLongTy
+    };
+    for (int Idx = 0; Idx < 6; ++Idx) {
+      uint64_t ToSize = Context.getTypeSize(PromoteTypes[Idx]);
+      if (FromSize < ToSize ||
+          (FromSize == ToSize && 
+           FromIsSigned == PromoteTypes[Idx]->isSignedIntegerType())) {
+        // We found the type that we can promote to. If this is the
+        // type we wanted, we have a promotion. Otherwise, no
+        // promotion.
+        return Context.getCanonicalType(ToType).getUnqualifiedType()
+          == Context.getCanonicalType(PromoteTypes[Idx]).getUnqualifiedType();
+      }
+    }
+  }
+
+  // An rvalue for an integral bit-field (9.6) can be converted to an
+  // rvalue of type int if int can represent all the values of the
+  // bit-field; otherwise, it can be converted to unsigned int if
+  // unsigned int can represent all the values of the bit-field. If
+  // the bit-field is larger yet, no integral promotion applies to
+  // it. If the bit-field has an enumerated type, it is treated as any
+  // other value of that type for promotion purposes (C++ 4.5p3).
+  // FIXME: We should delay checking of bit-fields until we actually perform the
+  // conversion.
+  using llvm::APSInt;
+  if (From)
+    if (FieldDecl *MemberDecl = From->getBitField()) {
+      APSInt BitWidth;
+      if (FromType->isIntegralType() && !FromType->isEnumeralType() &&
+          MemberDecl->getBitWidth()->isIntegerConstantExpr(BitWidth, Context)) {
+        APSInt ToSize(BitWidth.getBitWidth(), BitWidth.isUnsigned());
+        ToSize = Context.getTypeSize(ToType);
+        
+        // Are we promoting to an int from a bitfield that fits in an int?
+        if (BitWidth < ToSize ||
+            (FromType->isSignedIntegerType() && BitWidth <= ToSize)) {
+          return To->getKind() == BuiltinType::Int;
+        }
+        
+        // Are we promoting to an unsigned int from an unsigned bitfield
+        // that fits into an unsigned int?
+        if (FromType->isUnsignedIntegerType() && BitWidth <= ToSize) {
+          return To->getKind() == BuiltinType::UInt;
+        }
+        
+        return false;
+      }
+    }
+  
+  // An rvalue of type bool can be converted to an rvalue of type int,
+  // with false becoming zero and true becoming one (C++ 4.5p4).
+  if (FromType->isBooleanType() && To->getKind() == BuiltinType::Int) {
+    return true;
+  }
+
+  return false;
+}
+
+/// IsFloatingPointPromotion - Determines whether the conversion from
+/// FromType to ToType is a floating point promotion (C++ 4.6). If so,
+/// returns true and sets PromotedType to the promoted type.
+bool Sema::IsFloatingPointPromotion(QualType FromType, QualType ToType)
+{
+  /// An rvalue of type float can be converted to an rvalue of type
+  /// double. (C++ 4.6p1).
+  if (const BuiltinType *FromBuiltin = FromType->getAsBuiltinType())
+    if (const BuiltinType *ToBuiltin = ToType->getAsBuiltinType()) {
+      if (FromBuiltin->getKind() == BuiltinType::Float &&
+          ToBuiltin->getKind() == BuiltinType::Double)
+        return true;
+
+      // C99 6.3.1.5p1:
+      //   When a float is promoted to double or long double, or a
+      //   double is promoted to long double [...].
+      if (!getLangOptions().CPlusPlus &&
+          (FromBuiltin->getKind() == BuiltinType::Float ||
+           FromBuiltin->getKind() == BuiltinType::Double) &&
+          (ToBuiltin->getKind() == BuiltinType::LongDouble))
+        return true;
+    }
+
+  return false;
+}
+
+/// \brief Determine if a conversion is a complex promotion.
+///
+/// A complex promotion is defined as a complex -> complex conversion
+/// where the conversion between the underlying real types is a
+/// floating-point or integral promotion.
+bool Sema::IsComplexPromotion(QualType FromType, QualType ToType) {
+  const ComplexType *FromComplex = FromType->getAsComplexType();
+  if (!FromComplex)
+    return false;
+
+  const ComplexType *ToComplex = ToType->getAsComplexType();
+  if (!ToComplex)
+    return false;
+
+  return IsFloatingPointPromotion(FromComplex->getElementType(),
+                                  ToComplex->getElementType()) ||
+    IsIntegralPromotion(0, FromComplex->getElementType(),
+                        ToComplex->getElementType());
+}
+
+/// BuildSimilarlyQualifiedPointerType - In a pointer conversion from
+/// the pointer type FromPtr to a pointer to type ToPointee, with the
+/// same type qualifiers as FromPtr has on its pointee type. ToType,
+/// if non-empty, will be a pointer to ToType that may or may not have
+/// the right set of qualifiers on its pointee.
+static QualType 
+BuildSimilarlyQualifiedPointerType(const PointerType *FromPtr, 
+                                   QualType ToPointee, QualType ToType,
+                                   ASTContext &Context) {
+  QualType CanonFromPointee = Context.getCanonicalType(FromPtr->getPointeeType());
+  QualType CanonToPointee = Context.getCanonicalType(ToPointee);
+  unsigned Quals = CanonFromPointee.getCVRQualifiers();
+  
+  // Exact qualifier match -> return the pointer type we're converting to.  
+  if (CanonToPointee.getCVRQualifiers() == Quals) {
+    // ToType is exactly what we need. Return it.
+    if (ToType.getTypePtr())
+      return ToType;
+
+    // Build a pointer to ToPointee. It has the right qualifiers
+    // already.
+    return Context.getPointerType(ToPointee);
+  }
+
+  // Just build a canonical type that has the right qualifiers.
+  return Context.getPointerType(CanonToPointee.getQualifiedType(Quals));
+}
+
+/// IsPointerConversion - Determines whether the conversion of the
+/// expression From, which has the (possibly adjusted) type FromType,
+/// can be converted to the type ToType via a pointer conversion (C++
+/// 4.10). If so, returns true and places the converted type (that
+/// might differ from ToType in its cv-qualifiers at some level) into
+/// ConvertedType.
+///
+/// This routine also supports conversions to and from block pointers
+/// and conversions with Objective-C's 'id', 'id<protocols...>', and
+/// pointers to interfaces. FIXME: Once we've determined the
+/// appropriate overloading rules for Objective-C, we may want to
+/// split the Objective-C checks into a different routine; however,
+/// GCC seems to consider all of these conversions to be pointer
+/// conversions, so for now they live here. IncompatibleObjC will be
+/// set if the conversion is an allowed Objective-C conversion that
+/// should result in a warning.
+bool Sema::IsPointerConversion(Expr *From, QualType FromType, QualType ToType,
+                               QualType& ConvertedType,
+                               bool &IncompatibleObjC)
+{
+  IncompatibleObjC = false;
+  if (isObjCPointerConversion(FromType, ToType, ConvertedType, IncompatibleObjC))
+    return true;
+
+  // Conversion from a null pointer constant to any Objective-C pointer type. 
+  if (Context.isObjCObjectPointerType(ToType) && 
+      From->isNullPointerConstant(Context)) {
+    ConvertedType = ToType;
+    return true;
+  }
+
+  // Blocks: Block pointers can be converted to void*.
+  if (FromType->isBlockPointerType() && ToType->isPointerType() &&
+      ToType->getAsPointerType()->getPointeeType()->isVoidType()) {
+    ConvertedType = ToType;
+    return true;
+  }
+  // Blocks: A null pointer constant can be converted to a block
+  // pointer type.
+  if (ToType->isBlockPointerType() && From->isNullPointerConstant(Context)) {
+    ConvertedType = ToType;
+    return true;
+  }
+
+  // If the left-hand-side is nullptr_t, the right side can be a null
+  // pointer constant.
+  if (ToType->isNullPtrType() && From->isNullPointerConstant(Context)) {
+    ConvertedType = ToType;
+    return true;
+  }
+
+  const PointerType* ToTypePtr = ToType->getAsPointerType();
+  if (!ToTypePtr)
+    return false;
+
+  // A null pointer constant can be converted to a pointer type (C++ 4.10p1).
+  if (From->isNullPointerConstant(Context)) {
+    ConvertedType = ToType;
+    return true;
+  }
+
+  // Beyond this point, both types need to be pointers.
+  const PointerType *FromTypePtr = FromType->getAsPointerType();
+  if (!FromTypePtr)
+    return false;
+
+  QualType FromPointeeType = FromTypePtr->getPointeeType();
+  QualType ToPointeeType = ToTypePtr->getPointeeType();
+
+  // An rvalue of type "pointer to cv T," where T is an object type,
+  // can be converted to an rvalue of type "pointer to cv void" (C++
+  // 4.10p2).
+  if (FromPointeeType->isObjectType() && ToPointeeType->isVoidType()) {
+    ConvertedType = BuildSimilarlyQualifiedPointerType(FromTypePtr, 
+                                                       ToPointeeType,
+                                                       ToType, Context);
+    return true;
+  }
+
+  // When we're overloading in C, we allow a special kind of pointer
+  // conversion for compatible-but-not-identical pointee types.
+  if (!getLangOptions().CPlusPlus && 
+      Context.typesAreCompatible(FromPointeeType, ToPointeeType)) {
+    ConvertedType = BuildSimilarlyQualifiedPointerType(FromTypePtr, 
+                                                       ToPointeeType,
+                                                       ToType, Context);    
+    return true;
+  }
+
+  // C++ [conv.ptr]p3:
+  // 
+  //   An rvalue of type "pointer to cv D," where D is a class type,
+  //   can be converted to an rvalue of type "pointer to cv B," where
+  //   B is a base class (clause 10) of D. If B is an inaccessible
+  //   (clause 11) or ambiguous (10.2) base class of D, a program that
+  //   necessitates this conversion is ill-formed. The result of the
+  //   conversion is a pointer to the base class sub-object of the
+  //   derived class object. The null pointer value is converted to
+  //   the null pointer value of the destination type.
+  //
+  // Note that we do not check for ambiguity or inaccessibility
+  // here. That is handled by CheckPointerConversion.
+  if (getLangOptions().CPlusPlus &&
+      FromPointeeType->isRecordType() && ToPointeeType->isRecordType() &&
+      IsDerivedFrom(FromPointeeType, ToPointeeType)) {
+    ConvertedType = BuildSimilarlyQualifiedPointerType(FromTypePtr, 
+                                                       ToPointeeType,
+                                                       ToType, Context);
+    return true;
+  }
+
+  return false;
+}
+
+/// isObjCPointerConversion - Determines whether this is an
+/// Objective-C pointer conversion. Subroutine of IsPointerConversion,
+/// with the same arguments and return values.
+bool Sema::isObjCPointerConversion(QualType FromType, QualType ToType, 
+                                   QualType& ConvertedType,
+                                   bool &IncompatibleObjC) {
+  if (!getLangOptions().ObjC1)
+    return false;
+
+  // Conversions with Objective-C's id<...>.
+  if ((FromType->isObjCQualifiedIdType() || ToType->isObjCQualifiedIdType()) &&
+      ObjCQualifiedIdTypesAreCompatible(ToType, FromType, /*compare=*/false)) {
+    ConvertedType = ToType;
+    return true;
+  }
+
+  // Beyond this point, both types need to be pointers or block pointers.
+  QualType ToPointeeType;
+  const PointerType* ToTypePtr = ToType->getAsPointerType();
+  if (ToTypePtr)
+    ToPointeeType = ToTypePtr->getPointeeType();
+  else if (const BlockPointerType *ToBlockPtr = ToType->getAsBlockPointerType())
+    ToPointeeType = ToBlockPtr->getPointeeType();
+  else
+    return false;
+
+  QualType FromPointeeType;
+  const PointerType *FromTypePtr = FromType->getAsPointerType();
+  if (FromTypePtr)
+    FromPointeeType = FromTypePtr->getPointeeType();
+  else if (const BlockPointerType *FromBlockPtr 
+             = FromType->getAsBlockPointerType())
+    FromPointeeType = FromBlockPtr->getPointeeType();
+  else
+    return false;
+
+  // Objective C++: We're able to convert from a pointer to an
+  // interface to a pointer to a different interface.
+  const ObjCInterfaceType* FromIface = FromPointeeType->getAsObjCInterfaceType();
+  const ObjCInterfaceType* ToIface = ToPointeeType->getAsObjCInterfaceType();
+  if (FromIface && ToIface && 
+      Context.canAssignObjCInterfaces(ToIface, FromIface)) {
+    ConvertedType = BuildSimilarlyQualifiedPointerType(FromTypePtr,
+                                                       ToPointeeType,
+                                                       ToType, Context);
+    return true;
+  }
+
+  if (FromIface && ToIface && 
+      Context.canAssignObjCInterfaces(FromIface, ToIface)) {
+    // Okay: this is some kind of implicit downcast of Objective-C
+    // interfaces, which is permitted. However, we're going to
+    // complain about it.
+    IncompatibleObjC = true;
+    ConvertedType = BuildSimilarlyQualifiedPointerType(FromTypePtr,
+                                                       ToPointeeType,
+                                                       ToType, Context);
+    return true;
+  }
+
+  // Objective C++: We're able to convert between "id" and a pointer
+  // to any interface (in both directions).
+  if ((FromIface && Context.isObjCIdStructType(ToPointeeType))
+      || (ToIface && Context.isObjCIdStructType(FromPointeeType))) {
+    ConvertedType = BuildSimilarlyQualifiedPointerType(FromTypePtr, 
+                                                       ToPointeeType,
+                                                       ToType, Context);
+    return true;
+  } 
+
+  // Objective C++: Allow conversions between the Objective-C "id" and
+  // "Class", in either direction.
+  if ((Context.isObjCIdStructType(FromPointeeType) && 
+       Context.isObjCClassStructType(ToPointeeType)) ||
+      (Context.isObjCClassStructType(FromPointeeType) &&
+       Context.isObjCIdStructType(ToPointeeType))) {
+    ConvertedType = ToType;
+    return true;
+  }
+
+  // If we have pointers to pointers, recursively check whether this
+  // is an Objective-C conversion.
+  if (FromPointeeType->isPointerType() && ToPointeeType->isPointerType() &&
+      isObjCPointerConversion(FromPointeeType, ToPointeeType, ConvertedType,
+                              IncompatibleObjC)) {
+    // We always complain about this conversion.
+    IncompatibleObjC = true;
+    ConvertedType = ToType;
+    return true;
+  }
+
+  // If we have pointers to functions or blocks, check whether the only
+  // differences in the argument and result types are in Objective-C
+  // pointer conversions. If so, we permit the conversion (but
+  // complain about it).
+  const FunctionProtoType *FromFunctionType 
+    = FromPointeeType->getAsFunctionProtoType();
+  const FunctionProtoType *ToFunctionType
+    = ToPointeeType->getAsFunctionProtoType();
+  if (FromFunctionType && ToFunctionType) {
+    // If the function types are exactly the same, this isn't an
+    // Objective-C pointer conversion.
+    if (Context.getCanonicalType(FromPointeeType)
+          == Context.getCanonicalType(ToPointeeType))
+      return false;
+
+    // Perform the quick checks that will tell us whether these
+    // function types are obviously different.
+    if (FromFunctionType->getNumArgs() != ToFunctionType->getNumArgs() ||
+        FromFunctionType->isVariadic() != ToFunctionType->isVariadic() ||
+        FromFunctionType->getTypeQuals() != ToFunctionType->getTypeQuals())
+      return false;
+
+    bool HasObjCConversion = false;
+    if (Context.getCanonicalType(FromFunctionType->getResultType())
+          == Context.getCanonicalType(ToFunctionType->getResultType())) {
+      // Okay, the types match exactly. Nothing to do.
+    } else if (isObjCPointerConversion(FromFunctionType->getResultType(),
+                                       ToFunctionType->getResultType(),
+                                       ConvertedType, IncompatibleObjC)) {
+      // Okay, we have an Objective-C pointer conversion.
+      HasObjCConversion = true;
+    } else {
+      // Function types are too different. Abort.
+      return false;
+    }
+     
+    // Check argument types.
+    for (unsigned ArgIdx = 0, NumArgs = FromFunctionType->getNumArgs();
+         ArgIdx != NumArgs; ++ArgIdx) {
+      QualType FromArgType = FromFunctionType->getArgType(ArgIdx);
+      QualType ToArgType = ToFunctionType->getArgType(ArgIdx);
+      if (Context.getCanonicalType(FromArgType)
+            == Context.getCanonicalType(ToArgType)) {
+        // Okay, the types match exactly. Nothing to do.
+      } else if (isObjCPointerConversion(FromArgType, ToArgType,
+                                         ConvertedType, IncompatibleObjC)) {
+        // Okay, we have an Objective-C pointer conversion.
+        HasObjCConversion = true;
+      } else {
+        // Argument types are too different. Abort.
+        return false;
+      }
+    }
+
+    if (HasObjCConversion) {
+      // We had an Objective-C conversion. Allow this pointer
+      // conversion, but complain about it.
+      ConvertedType = ToType;
+      IncompatibleObjC = true;
+      return true;
+    }
+  }
+
+  return false;
+}
+
+/// CheckPointerConversion - Check the pointer conversion from the
+/// expression From to the type ToType. This routine checks for
+/// ambiguous (FIXME: or inaccessible) derived-to-base pointer
+/// conversions for which IsPointerConversion has already returned
+/// true. It returns true and produces a diagnostic if there was an
+/// error, or returns false otherwise.
+bool Sema::CheckPointerConversion(Expr *From, QualType ToType) {
+  QualType FromType = From->getType();
+
+  if (const PointerType *FromPtrType = FromType->getAsPointerType())
+    if (const PointerType *ToPtrType = ToType->getAsPointerType()) {
+      QualType FromPointeeType = FromPtrType->getPointeeType(),
+               ToPointeeType   = ToPtrType->getPointeeType();
+
+      // Objective-C++ conversions are always okay.
+      // FIXME: We should have a different class of conversions for the
+      // Objective-C++ implicit conversions.
+      if (Context.isObjCIdStructType(FromPointeeType) || 
+          Context.isObjCIdStructType(ToPointeeType) ||
+          Context.isObjCClassStructType(FromPointeeType) ||
+          Context.isObjCClassStructType(ToPointeeType))
+        return false;
+
+      if (FromPointeeType->isRecordType() &&
+          ToPointeeType->isRecordType()) {
+        // We must have a derived-to-base conversion. Check an
+        // ambiguous or inaccessible conversion.
+        return CheckDerivedToBaseConversion(FromPointeeType, ToPointeeType,
+                                            From->getExprLoc(),
+                                            From->getSourceRange());
+      }
+    }
+
+  return false;
+}
+
+/// IsMemberPointerConversion - Determines whether the conversion of the
+/// expression From, which has the (possibly adjusted) type FromType, can be
+/// converted to the type ToType via a member pointer conversion (C++ 4.11).
+/// If so, returns true and places the converted type (that might differ from
+/// ToType in its cv-qualifiers at some level) into ConvertedType.
+bool Sema::IsMemberPointerConversion(Expr *From, QualType FromType,
+                                     QualType ToType, QualType &ConvertedType)
+{
+  const MemberPointerType *ToTypePtr = ToType->getAsMemberPointerType();
+  if (!ToTypePtr)
+    return false;
+
+  // A null pointer constant can be converted to a member pointer (C++ 4.11p1)
+  if (From->isNullPointerConstant(Context)) {
+    ConvertedType = ToType;
+    return true;
+  }
+
+  // Otherwise, both types have to be member pointers.
+  const MemberPointerType *FromTypePtr = FromType->getAsMemberPointerType();
+  if (!FromTypePtr)
+    return false;
+
+  // A pointer to member of B can be converted to a pointer to member of D,
+  // where D is derived from B (C++ 4.11p2).
+  QualType FromClass(FromTypePtr->getClass(), 0);
+  QualType ToClass(ToTypePtr->getClass(), 0);
+  // FIXME: What happens when these are dependent? Is this function even called?
+
+  if (IsDerivedFrom(ToClass, FromClass)) {
+    ConvertedType = Context.getMemberPointerType(FromTypePtr->getPointeeType(),
+                                                 ToClass.getTypePtr());
+    return true;
+  }
+
+  return false;
+}
+
+/// CheckMemberPointerConversion - Check the member pointer conversion from the
+/// expression From to the type ToType. This routine checks for ambiguous or
+/// virtual (FIXME: or inaccessible) base-to-derived member pointer conversions
+/// for which IsMemberPointerConversion has already returned true. It returns
+/// true and produces a diagnostic if there was an error, or returns false
+/// otherwise.
+bool Sema::CheckMemberPointerConversion(Expr *From, QualType ToType) {
+  QualType FromType = From->getType();
+  const MemberPointerType *FromPtrType = FromType->getAsMemberPointerType();
+  if (!FromPtrType)
+    return false;
+
+  const MemberPointerType *ToPtrType = ToType->getAsMemberPointerType();
+  assert(ToPtrType && "No member pointer cast has a target type "
+                      "that is not a member pointer.");
+
+  QualType FromClass = QualType(FromPtrType->getClass(), 0);
+  QualType ToClass   = QualType(ToPtrType->getClass(), 0);
+
+  // FIXME: What about dependent types?
+  assert(FromClass->isRecordType() && "Pointer into non-class.");
+  assert(ToClass->isRecordType() && "Pointer into non-class.");
+
+  BasePaths Paths(/*FindAmbiguities=*/true, /*RecordPaths=*/false,
+                  /*DetectVirtual=*/true);
+  bool DerivationOkay = IsDerivedFrom(ToClass, FromClass, Paths);
+  assert(DerivationOkay &&
+         "Should not have been called if derivation isn't OK.");
+  (void)DerivationOkay;
+
+  if (Paths.isAmbiguous(Context.getCanonicalType(FromClass).
+                                  getUnqualifiedType())) {
+    // Derivation is ambiguous. Redo the check to find the exact paths.
+    Paths.clear();
+    Paths.setRecordingPaths(true);
+    bool StillOkay = IsDerivedFrom(ToClass, FromClass, Paths);
+    assert(StillOkay && "Derivation changed due to quantum fluctuation.");
+    (void)StillOkay;
+
+    std::string PathDisplayStr = getAmbiguousPathsDisplayString(Paths);
+    Diag(From->getExprLoc(), diag::err_ambiguous_memptr_conv)
+      << 0 << FromClass << ToClass << PathDisplayStr << From->getSourceRange();
+    return true;
+  }
+
+  if (const RecordType *VBase = Paths.getDetectedVirtual()) {
+    Diag(From->getExprLoc(), diag::err_memptr_conv_via_virtual)
+      << FromClass << ToClass << QualType(VBase, 0)
+      << From->getSourceRange();
+    return true;
+  }
+
+  return false;
+}
+
+/// IsQualificationConversion - Determines whether the conversion from
+/// an rvalue of type FromType to ToType is a qualification conversion
+/// (C++ 4.4).
+bool 
+Sema::IsQualificationConversion(QualType FromType, QualType ToType)
+{
+  FromType = Context.getCanonicalType(FromType);
+  ToType = Context.getCanonicalType(ToType);
+
+  // If FromType and ToType are the same type, this is not a
+  // qualification conversion.
+  if (FromType == ToType)
+    return false;
+
+  // (C++ 4.4p4):
+  //   A conversion can add cv-qualifiers at levels other than the first
+  //   in multi-level pointers, subject to the following rules: [...]
+  bool PreviousToQualsIncludeConst = true;
+  bool UnwrappedAnyPointer = false;
+  while (UnwrapSimilarPointerTypes(FromType, ToType)) {
+    // Within each iteration of the loop, we check the qualifiers to
+    // determine if this still looks like a qualification
+    // conversion. Then, if all is well, we unwrap one more level of
+    // pointers or pointers-to-members and do it all again
+    // until there are no more pointers or pointers-to-members left to
+    // unwrap.
+    UnwrappedAnyPointer = true;
+
+    //   -- for every j > 0, if const is in cv 1,j then const is in cv
+    //      2,j, and similarly for volatile.
+    if (!ToType.isAtLeastAsQualifiedAs(FromType))
+      return false;
+    
+    //   -- if the cv 1,j and cv 2,j are different, then const is in
+    //      every cv for 0 < k < j.
+    if (FromType.getCVRQualifiers() != ToType.getCVRQualifiers()
+        && !PreviousToQualsIncludeConst)
+      return false;
+    
+    // Keep track of whether all prior cv-qualifiers in the "to" type
+    // include const.
+    PreviousToQualsIncludeConst 
+      = PreviousToQualsIncludeConst && ToType.isConstQualified();
+  }
+
+  // We are left with FromType and ToType being the pointee types
+  // after unwrapping the original FromType and ToType the same number
+  // of types. If we unwrapped any pointers, and if FromType and
+  // ToType have the same unqualified type (since we checked
+  // qualifiers above), then this is a qualification conversion.
+  return UnwrappedAnyPointer &&
+    FromType.getUnqualifiedType() == ToType.getUnqualifiedType();
+}
+
+/// Determines whether there is a user-defined conversion sequence
+/// (C++ [over.ics.user]) that converts expression From to the type
+/// ToType. If such a conversion exists, User will contain the
+/// user-defined conversion sequence that performs such a conversion
+/// and this routine will return true. Otherwise, this routine returns
+/// false and User is unspecified.
+///
+/// \param AllowConversionFunctions true if the conversion should
+/// consider conversion functions at all. If false, only constructors
+/// will be considered.
+///
+/// \param AllowExplicit  true if the conversion should consider C++0x
+/// "explicit" conversion functions as well as non-explicit conversion
+/// functions (C++0x [class.conv.fct]p2).
+///
+/// \param ForceRValue  true if the expression should be treated as an rvalue
+/// for overload resolution.
+bool Sema::IsUserDefinedConversion(Expr *From, QualType ToType, 
+                                   UserDefinedConversionSequence& User,
+                                   bool AllowConversionFunctions,
+                                   bool AllowExplicit, bool ForceRValue)
+{
+  OverloadCandidateSet CandidateSet;
+  if (const RecordType *ToRecordType = ToType->getAsRecordType()) {
+    if (CXXRecordDecl *ToRecordDecl 
+          = dyn_cast<CXXRecordDecl>(ToRecordType->getDecl())) {
+      // C++ [over.match.ctor]p1:
+      //   When objects of class type are direct-initialized (8.5), or
+      //   copy-initialized from an expression of the same or a
+      //   derived class type (8.5), overload resolution selects the
+      //   constructor. [...] For copy-initialization, the candidate
+      //   functions are all the converting constructors (12.3.1) of
+      //   that class. The argument list is the expression-list within
+      //   the parentheses of the initializer.
+      DeclarationName ConstructorName 
+        = Context.DeclarationNames.getCXXConstructorName(
+                          Context.getCanonicalType(ToType).getUnqualifiedType());
+      DeclContext::lookup_iterator Con, ConEnd;
+      for (llvm::tie(Con, ConEnd) 
+             = ToRecordDecl->lookup(Context, ConstructorName);
+           Con != ConEnd; ++Con) {
+        CXXConstructorDecl *Constructor = cast<CXXConstructorDecl>(*Con);
+        if (Constructor->isConvertingConstructor())
+          AddOverloadCandidate(Constructor, &From, 1, CandidateSet,
+                               /*SuppressUserConversions=*/true, ForceRValue);
+      }
+    }
+  }
+
+  if (!AllowConversionFunctions) {
+    // Don't allow any conversion functions to enter the overload set.
+  } else if (const RecordType *FromRecordType 
+               = From->getType()->getAsRecordType()) {
+    if (CXXRecordDecl *FromRecordDecl 
+          = dyn_cast<CXXRecordDecl>(FromRecordType->getDecl())) {
+      // Add all of the conversion functions as candidates.
+      // FIXME: Look for conversions in base classes!
+      OverloadedFunctionDecl *Conversions 
+        = FromRecordDecl->getConversionFunctions();
+      for (OverloadedFunctionDecl::function_iterator Func 
+             = Conversions->function_begin();
+           Func != Conversions->function_end(); ++Func) {
+        CXXConversionDecl *Conv = cast<CXXConversionDecl>(*Func);
+        if (AllowExplicit || !Conv->isExplicit())
+          AddConversionCandidate(Conv, From, ToType, CandidateSet);
+      }
+    }
+  }
+
+  OverloadCandidateSet::iterator Best;
+  switch (BestViableFunction(CandidateSet, Best)) {
+    case OR_Success:
+      // Record the standard conversion we used and the conversion function.
+      if (CXXConstructorDecl *Constructor 
+            = dyn_cast<CXXConstructorDecl>(Best->Function)) {
+        // C++ [over.ics.user]p1:
+        //   If the user-defined conversion is specified by a
+        //   constructor (12.3.1), the initial standard conversion
+        //   sequence converts the source type to the type required by
+        //   the argument of the constructor.
+        //
+        // FIXME: What about ellipsis conversions?
+        QualType ThisType = Constructor->getThisType(Context);
+        User.Before = Best->Conversions[0].Standard;
+        User.ConversionFunction = Constructor;
+        User.After.setAsIdentityConversion();
+        User.After.FromTypePtr 
+          = ThisType->getAsPointerType()->getPointeeType().getAsOpaquePtr();
+        User.After.ToTypePtr = ToType.getAsOpaquePtr();
+        return true;
+      } else if (CXXConversionDecl *Conversion
+                   = dyn_cast<CXXConversionDecl>(Best->Function)) {
+        // C++ [over.ics.user]p1:
+        //
+        //   [...] If the user-defined conversion is specified by a
+        //   conversion function (12.3.2), the initial standard
+        //   conversion sequence converts the source type to the
+        //   implicit object parameter of the conversion function.
+        User.Before = Best->Conversions[0].Standard;
+        User.ConversionFunction = Conversion;
+        
+        // C++ [over.ics.user]p2: 
+        //   The second standard conversion sequence converts the
+        //   result of the user-defined conversion to the target type
+        //   for the sequence. Since an implicit conversion sequence
+        //   is an initialization, the special rules for
+        //   initialization by user-defined conversion apply when
+        //   selecting the best user-defined conversion for a
+        //   user-defined conversion sequence (see 13.3.3 and
+        //   13.3.3.1).
+        User.After = Best->FinalConversion;
+        return true;
+      } else {
+        assert(false && "Not a constructor or conversion function?");
+        return false;
+      }
+      
+    case OR_No_Viable_Function:
+    case OR_Deleted:
+      // No conversion here! We're done.
+      return false;
+
+    case OR_Ambiguous:
+      // FIXME: See C++ [over.best.ics]p10 for the handling of
+      // ambiguous conversion sequences.
+      return false;
+    }
+
+  return false;
+}
+
+/// CompareImplicitConversionSequences - Compare two implicit
+/// conversion sequences to determine whether one is better than the
+/// other or if they are indistinguishable (C++ 13.3.3.2).
+ImplicitConversionSequence::CompareKind 
+Sema::CompareImplicitConversionSequences(const ImplicitConversionSequence& ICS1,
+                                         const ImplicitConversionSequence& ICS2)
+{
+  // (C++ 13.3.3.2p2): When comparing the basic forms of implicit
+  // conversion sequences (as defined in 13.3.3.1)
+  //   -- a standard conversion sequence (13.3.3.1.1) is a better
+  //      conversion sequence than a user-defined conversion sequence or
+  //      an ellipsis conversion sequence, and
+  //   -- a user-defined conversion sequence (13.3.3.1.2) is a better
+  //      conversion sequence than an ellipsis conversion sequence
+  //      (13.3.3.1.3).
+  // 
+  if (ICS1.ConversionKind < ICS2.ConversionKind)
+    return ImplicitConversionSequence::Better;
+  else if (ICS2.ConversionKind < ICS1.ConversionKind)
+    return ImplicitConversionSequence::Worse;
+
+  // Two implicit conversion sequences of the same form are
+  // indistinguishable conversion sequences unless one of the
+  // following rules apply: (C++ 13.3.3.2p3):
+  if (ICS1.ConversionKind == ImplicitConversionSequence::StandardConversion)
+    return CompareStandardConversionSequences(ICS1.Standard, ICS2.Standard);
+  else if (ICS1.ConversionKind == 
+             ImplicitConversionSequence::UserDefinedConversion) {
+    // User-defined conversion sequence U1 is a better conversion
+    // sequence than another user-defined conversion sequence U2 if
+    // they contain the same user-defined conversion function or
+    // constructor and if the second standard conversion sequence of
+    // U1 is better than the second standard conversion sequence of
+    // U2 (C++ 13.3.3.2p3).
+    if (ICS1.UserDefined.ConversionFunction == 
+          ICS2.UserDefined.ConversionFunction)
+      return CompareStandardConversionSequences(ICS1.UserDefined.After,
+                                                ICS2.UserDefined.After);
+  }
+
+  return ImplicitConversionSequence::Indistinguishable;
+}
+
+/// CompareStandardConversionSequences - Compare two standard
+/// conversion sequences to determine whether one is better than the
+/// other or if they are indistinguishable (C++ 13.3.3.2p3).
+ImplicitConversionSequence::CompareKind 
+Sema::CompareStandardConversionSequences(const StandardConversionSequence& SCS1,
+                                         const StandardConversionSequence& SCS2)
+{
+  // Standard conversion sequence S1 is a better conversion sequence
+  // than standard conversion sequence S2 if (C++ 13.3.3.2p3):
+
+  //  -- S1 is a proper subsequence of S2 (comparing the conversion
+  //     sequences in the canonical form defined by 13.3.3.1.1,
+  //     excluding any Lvalue Transformation; the identity conversion
+  //     sequence is considered to be a subsequence of any
+  //     non-identity conversion sequence) or, if not that,
+  if (SCS1.Second == SCS2.Second && SCS1.Third == SCS2.Third)
+    // Neither is a proper subsequence of the other. Do nothing.
+    ;
+  else if ((SCS1.Second == ICK_Identity && SCS1.Third == SCS2.Third) ||
+           (SCS1.Third == ICK_Identity && SCS1.Second == SCS2.Second) ||
+           (SCS1.Second == ICK_Identity && 
+            SCS1.Third == ICK_Identity))
+    // SCS1 is a proper subsequence of SCS2.
+    return ImplicitConversionSequence::Better;
+  else if ((SCS2.Second == ICK_Identity && SCS2.Third == SCS1.Third) ||
+           (SCS2.Third == ICK_Identity && SCS2.Second == SCS1.Second) ||
+           (SCS2.Second == ICK_Identity && 
+            SCS2.Third == ICK_Identity))
+    // SCS2 is a proper subsequence of SCS1.
+    return ImplicitConversionSequence::Worse;
+
+  //  -- the rank of S1 is better than the rank of S2 (by the rules
+  //     defined below), or, if not that,
+  ImplicitConversionRank Rank1 = SCS1.getRank();
+  ImplicitConversionRank Rank2 = SCS2.getRank();
+  if (Rank1 < Rank2)
+    return ImplicitConversionSequence::Better;
+  else if (Rank2 < Rank1)
+    return ImplicitConversionSequence::Worse;
+
+  // (C++ 13.3.3.2p4): Two conversion sequences with the same rank
+  // are indistinguishable unless one of the following rules
+  // applies:
+  
+  //   A conversion that is not a conversion of a pointer, or
+  //   pointer to member, to bool is better than another conversion
+  //   that is such a conversion.
+  if (SCS1.isPointerConversionToBool() != SCS2.isPointerConversionToBool())
+    return SCS2.isPointerConversionToBool()
+             ? ImplicitConversionSequence::Better
+             : ImplicitConversionSequence::Worse;
+
+  // C++ [over.ics.rank]p4b2:
+  //
+  //   If class B is derived directly or indirectly from class A,
+  //   conversion of B* to A* is better than conversion of B* to
+  //   void*, and conversion of A* to void* is better than conversion
+  //   of B* to void*.
+  bool SCS1ConvertsToVoid 
+    = SCS1.isPointerConversionToVoidPointer(Context);
+  bool SCS2ConvertsToVoid 
+    = SCS2.isPointerConversionToVoidPointer(Context);
+  if (SCS1ConvertsToVoid != SCS2ConvertsToVoid) {
+    // Exactly one of the conversion sequences is a conversion to
+    // a void pointer; it's the worse conversion.
+    return SCS2ConvertsToVoid ? ImplicitConversionSequence::Better
+                              : ImplicitConversionSequence::Worse;
+  } else if (!SCS1ConvertsToVoid && !SCS2ConvertsToVoid) {
+    // Neither conversion sequence converts to a void pointer; compare
+    // their derived-to-base conversions.
+    if (ImplicitConversionSequence::CompareKind DerivedCK
+          = CompareDerivedToBaseConversions(SCS1, SCS2))
+      return DerivedCK;
+  } else if (SCS1ConvertsToVoid && SCS2ConvertsToVoid) {
+    // Both conversion sequences are conversions to void
+    // pointers. Compare the source types to determine if there's an
+    // inheritance relationship in their sources.
+    QualType FromType1 = QualType::getFromOpaquePtr(SCS1.FromTypePtr);
+    QualType FromType2 = QualType::getFromOpaquePtr(SCS2.FromTypePtr);
+
+    // Adjust the types we're converting from via the array-to-pointer
+    // conversion, if we need to.
+    if (SCS1.First == ICK_Array_To_Pointer)
+      FromType1 = Context.getArrayDecayedType(FromType1);
+    if (SCS2.First == ICK_Array_To_Pointer)
+      FromType2 = Context.getArrayDecayedType(FromType2);
+
+    QualType FromPointee1 
+      = FromType1->getAsPointerType()->getPointeeType().getUnqualifiedType();
+    QualType FromPointee2
+      = FromType2->getAsPointerType()->getPointeeType().getUnqualifiedType();
+
+    if (IsDerivedFrom(FromPointee2, FromPointee1))
+      return ImplicitConversionSequence::Better;
+    else if (IsDerivedFrom(FromPointee1, FromPointee2))
+      return ImplicitConversionSequence::Worse;
+
+    // Objective-C++: If one interface is more specific than the
+    // other, it is the better one.
+    const ObjCInterfaceType* FromIface1 = FromPointee1->getAsObjCInterfaceType();
+    const ObjCInterfaceType* FromIface2 = FromPointee2->getAsObjCInterfaceType();
+    if (FromIface1 && FromIface1) {
+      if (Context.canAssignObjCInterfaces(FromIface2, FromIface1))
+        return ImplicitConversionSequence::Better;
+      else if (Context.canAssignObjCInterfaces(FromIface1, FromIface2))
+        return ImplicitConversionSequence::Worse;
+    }
+  }
+
+  // Compare based on qualification conversions (C++ 13.3.3.2p3,
+  // bullet 3).
+  if (ImplicitConversionSequence::CompareKind QualCK 
+        = CompareQualificationConversions(SCS1, SCS2))
+    return QualCK;
+
+  if (SCS1.ReferenceBinding && SCS2.ReferenceBinding) {
+    // C++0x [over.ics.rank]p3b4:
+    //   -- S1 and S2 are reference bindings (8.5.3) and neither refers to an
+    //      implicit object parameter of a non-static member function declared
+    //      without a ref-qualifier, and S1 binds an rvalue reference to an
+    //      rvalue and S2 binds an lvalue reference.
+    // FIXME: We don't know if we're dealing with the implicit object parameter,
+    // or if the member function in this case has a ref qualifier.
+    // (Of course, we don't have ref qualifiers yet.)
+    if (SCS1.RRefBinding != SCS2.RRefBinding)
+      return SCS1.RRefBinding ? ImplicitConversionSequence::Better
+                              : ImplicitConversionSequence::Worse;
+
+    // C++ [over.ics.rank]p3b4:
+    //   -- S1 and S2 are reference bindings (8.5.3), and the types to
+    //      which the references refer are the same type except for
+    //      top-level cv-qualifiers, and the type to which the reference
+    //      initialized by S2 refers is more cv-qualified than the type
+    //      to which the reference initialized by S1 refers.
+    QualType T1 = QualType::getFromOpaquePtr(SCS1.ToTypePtr);
+    QualType T2 = QualType::getFromOpaquePtr(SCS2.ToTypePtr);
+    T1 = Context.getCanonicalType(T1);
+    T2 = Context.getCanonicalType(T2);
+    if (T1.getUnqualifiedType() == T2.getUnqualifiedType()) {
+      if (T2.isMoreQualifiedThan(T1))
+        return ImplicitConversionSequence::Better;
+      else if (T1.isMoreQualifiedThan(T2))
+        return ImplicitConversionSequence::Worse;
+    }
+  }
+
+  return ImplicitConversionSequence::Indistinguishable;
+}
+
+/// CompareQualificationConversions - Compares two standard conversion
+/// sequences to determine whether they can be ranked based on their
+/// qualification conversions (C++ 13.3.3.2p3 bullet 3). 
+ImplicitConversionSequence::CompareKind 
+Sema::CompareQualificationConversions(const StandardConversionSequence& SCS1,
+                                      const StandardConversionSequence& SCS2)
+{
+  // C++ 13.3.3.2p3:
+  //  -- S1 and S2 differ only in their qualification conversion and
+  //     yield similar types T1 and T2 (C++ 4.4), respectively, and the
+  //     cv-qualification signature of type T1 is a proper subset of
+  //     the cv-qualification signature of type T2, and S1 is not the
+  //     deprecated string literal array-to-pointer conversion (4.2).
+  if (SCS1.First != SCS2.First || SCS1.Second != SCS2.Second ||
+      SCS1.Third != SCS2.Third || SCS1.Third != ICK_Qualification)
+    return ImplicitConversionSequence::Indistinguishable;
+
+  // FIXME: the example in the standard doesn't use a qualification
+  // conversion (!)
+  QualType T1 = QualType::getFromOpaquePtr(SCS1.ToTypePtr);
+  QualType T2 = QualType::getFromOpaquePtr(SCS2.ToTypePtr);
+  T1 = Context.getCanonicalType(T1);
+  T2 = Context.getCanonicalType(T2);
+
+  // If the types are the same, we won't learn anything by unwrapped
+  // them.
+  if (T1.getUnqualifiedType() == T2.getUnqualifiedType())
+    return ImplicitConversionSequence::Indistinguishable;
+
+  ImplicitConversionSequence::CompareKind Result 
+    = ImplicitConversionSequence::Indistinguishable;
+  while (UnwrapSimilarPointerTypes(T1, T2)) {
+    // Within each iteration of the loop, we check the qualifiers to
+    // determine if this still looks like a qualification
+    // conversion. Then, if all is well, we unwrap one more level of
+    // pointers or pointers-to-members and do it all again
+    // until there are no more pointers or pointers-to-members left
+    // to unwrap. This essentially mimics what
+    // IsQualificationConversion does, but here we're checking for a
+    // strict subset of qualifiers.
+    if (T1.getCVRQualifiers() == T2.getCVRQualifiers())
+      // The qualifiers are the same, so this doesn't tell us anything
+      // about how the sequences rank.
+      ;
+    else if (T2.isMoreQualifiedThan(T1)) {
+      // T1 has fewer qualifiers, so it could be the better sequence.
+      if (Result == ImplicitConversionSequence::Worse)
+        // Neither has qualifiers that are a subset of the other's
+        // qualifiers.
+        return ImplicitConversionSequence::Indistinguishable;
+      
+      Result = ImplicitConversionSequence::Better;
+    } else if (T1.isMoreQualifiedThan(T2)) {
+      // T2 has fewer qualifiers, so it could be the better sequence.
+      if (Result == ImplicitConversionSequence::Better)
+        // Neither has qualifiers that are a subset of the other's
+        // qualifiers.
+        return ImplicitConversionSequence::Indistinguishable;
+      
+      Result = ImplicitConversionSequence::Worse;
+    } else {
+      // Qualifiers are disjoint.
+      return ImplicitConversionSequence::Indistinguishable;
+    }
+
+    // If the types after this point are equivalent, we're done.
+    if (T1.getUnqualifiedType() == T2.getUnqualifiedType())
+      break;
+  }
+
+  // Check that the winning standard conversion sequence isn't using
+  // the deprecated string literal array to pointer conversion.
+  switch (Result) {
+  case ImplicitConversionSequence::Better:
+    if (SCS1.Deprecated)
+      Result = ImplicitConversionSequence::Indistinguishable;
+    break;
+
+  case ImplicitConversionSequence::Indistinguishable:
+    break;
+
+  case ImplicitConversionSequence::Worse:
+    if (SCS2.Deprecated)
+      Result = ImplicitConversionSequence::Indistinguishable;
+    break;
+  }
+
+  return Result;
+}
+
+/// CompareDerivedToBaseConversions - Compares two standard conversion
+/// sequences to determine whether they can be ranked based on their
+/// various kinds of derived-to-base conversions (C++
+/// [over.ics.rank]p4b3).  As part of these checks, we also look at
+/// conversions between Objective-C interface types.
+ImplicitConversionSequence::CompareKind
+Sema::CompareDerivedToBaseConversions(const StandardConversionSequence& SCS1,
+                                      const StandardConversionSequence& SCS2) {
+  QualType FromType1 = QualType::getFromOpaquePtr(SCS1.FromTypePtr);
+  QualType ToType1 = QualType::getFromOpaquePtr(SCS1.ToTypePtr);
+  QualType FromType2 = QualType::getFromOpaquePtr(SCS2.FromTypePtr);
+  QualType ToType2 = QualType::getFromOpaquePtr(SCS2.ToTypePtr);
+
+  // Adjust the types we're converting from via the array-to-pointer
+  // conversion, if we need to.
+  if (SCS1.First == ICK_Array_To_Pointer)
+    FromType1 = Context.getArrayDecayedType(FromType1);
+  if (SCS2.First == ICK_Array_To_Pointer)
+    FromType2 = Context.getArrayDecayedType(FromType2);
+
+  // Canonicalize all of the types.
+  FromType1 = Context.getCanonicalType(FromType1);
+  ToType1 = Context.getCanonicalType(ToType1);
+  FromType2 = Context.getCanonicalType(FromType2);
+  ToType2 = Context.getCanonicalType(ToType2);
+
+  // C++ [over.ics.rank]p4b3:
+  //
+  //   If class B is derived directly or indirectly from class A and
+  //   class C is derived directly or indirectly from B,
+  //
+  // For Objective-C, we let A, B, and C also be Objective-C
+  // interfaces.
+
+  // Compare based on pointer conversions.
+  if (SCS1.Second == ICK_Pointer_Conversion && 
+      SCS2.Second == ICK_Pointer_Conversion &&
+      /*FIXME: Remove if Objective-C id conversions get their own rank*/
+      FromType1->isPointerType() && FromType2->isPointerType() &&
+      ToType1->isPointerType() && ToType2->isPointerType()) {
+    QualType FromPointee1 
+      = FromType1->getAsPointerType()->getPointeeType().getUnqualifiedType();
+    QualType ToPointee1 
+      = ToType1->getAsPointerType()->getPointeeType().getUnqualifiedType();
+    QualType FromPointee2
+      = FromType2->getAsPointerType()->getPointeeType().getUnqualifiedType();
+    QualType ToPointee2
+      = ToType2->getAsPointerType()->getPointeeType().getUnqualifiedType();
+
+    const ObjCInterfaceType* FromIface1 = FromPointee1->getAsObjCInterfaceType();
+    const ObjCInterfaceType* FromIface2 = FromPointee2->getAsObjCInterfaceType();
+    const ObjCInterfaceType* ToIface1 = ToPointee1->getAsObjCInterfaceType();
+    const ObjCInterfaceType* ToIface2 = ToPointee2->getAsObjCInterfaceType();
+
+    //   -- conversion of C* to B* is better than conversion of C* to A*,
+    if (FromPointee1 == FromPointee2 && ToPointee1 != ToPointee2) {
+      if (IsDerivedFrom(ToPointee1, ToPointee2))
+        return ImplicitConversionSequence::Better;
+      else if (IsDerivedFrom(ToPointee2, ToPointee1))
+        return ImplicitConversionSequence::Worse;
+
+      if (ToIface1 && ToIface2) {
+        if (Context.canAssignObjCInterfaces(ToIface2, ToIface1))
+          return ImplicitConversionSequence::Better;
+        else if (Context.canAssignObjCInterfaces(ToIface1, ToIface2))
+          return ImplicitConversionSequence::Worse;
+      }
+    }
+
+    //   -- conversion of B* to A* is better than conversion of C* to A*,
+    if (FromPointee1 != FromPointee2 && ToPointee1 == ToPointee2) {
+      if (IsDerivedFrom(FromPointee2, FromPointee1))
+        return ImplicitConversionSequence::Better;
+      else if (IsDerivedFrom(FromPointee1, FromPointee2))
+        return ImplicitConversionSequence::Worse;
+      
+      if (FromIface1 && FromIface2) {
+        if (Context.canAssignObjCInterfaces(FromIface1, FromIface2))
+          return ImplicitConversionSequence::Better;
+        else if (Context.canAssignObjCInterfaces(FromIface2, FromIface1))
+          return ImplicitConversionSequence::Worse;
+      }
+    }
+  }
+
+  // Compare based on reference bindings.
+  if (SCS1.ReferenceBinding && SCS2.ReferenceBinding &&
+      SCS1.Second == ICK_Derived_To_Base) {
+    //   -- binding of an expression of type C to a reference of type
+    //      B& is better than binding an expression of type C to a
+    //      reference of type A&,
+    if (FromType1.getUnqualifiedType() == FromType2.getUnqualifiedType() &&
+        ToType1.getUnqualifiedType() != ToType2.getUnqualifiedType()) {
+      if (IsDerivedFrom(ToType1, ToType2))
+        return ImplicitConversionSequence::Better;
+      else if (IsDerivedFrom(ToType2, ToType1))
+        return ImplicitConversionSequence::Worse;
+    }
+
+    //   -- binding of an expression of type B to a reference of type
+    //      A& is better than binding an expression of type C to a
+    //      reference of type A&,
+    if (FromType1.getUnqualifiedType() != FromType2.getUnqualifiedType() &&
+        ToType1.getUnqualifiedType() == ToType2.getUnqualifiedType()) {
+      if (IsDerivedFrom(FromType2, FromType1))
+        return ImplicitConversionSequence::Better;
+      else if (IsDerivedFrom(FromType1, FromType2))
+        return ImplicitConversionSequence::Worse;
+    }
+  }
+
+
+  // FIXME: conversion of A::* to B::* is better than conversion of
+  // A::* to C::*,
+
+  // FIXME: conversion of B::* to C::* is better than conversion of
+  // A::* to C::*, and
+
+  if (SCS1.CopyConstructor && SCS2.CopyConstructor &&
+      SCS1.Second == ICK_Derived_To_Base) {
+    //   -- conversion of C to B is better than conversion of C to A,
+    if (FromType1.getUnqualifiedType() == FromType2.getUnqualifiedType() &&
+        ToType1.getUnqualifiedType() != ToType2.getUnqualifiedType()) {
+      if (IsDerivedFrom(ToType1, ToType2))
+        return ImplicitConversionSequence::Better;
+      else if (IsDerivedFrom(ToType2, ToType1))
+        return ImplicitConversionSequence::Worse;
+    }
+
+    //   -- conversion of B to A is better than conversion of C to A.
+    if (FromType1.getUnqualifiedType() != FromType2.getUnqualifiedType() &&
+        ToType1.getUnqualifiedType() == ToType2.getUnqualifiedType()) {
+      if (IsDerivedFrom(FromType2, FromType1))
+        return ImplicitConversionSequence::Better;
+      else if (IsDerivedFrom(FromType1, FromType2))
+        return ImplicitConversionSequence::Worse;
+    }
+  }
+
+  return ImplicitConversionSequence::Indistinguishable;
+}
+
+/// TryCopyInitialization - Try to copy-initialize a value of type
+/// ToType from the expression From. Return the implicit conversion
+/// sequence required to pass this argument, which may be a bad
+/// conversion sequence (meaning that the argument cannot be passed to
+/// a parameter of this type). If @p SuppressUserConversions, then we
+/// do not permit any user-defined conversion sequences. If @p ForceRValue,
+/// then we treat @p From as an rvalue, even if it is an lvalue.
+ImplicitConversionSequence 
+Sema::TryCopyInitialization(Expr *From, QualType ToType, 
+                            bool SuppressUserConversions, bool ForceRValue) {
+  if (ToType->isReferenceType()) {
+    ImplicitConversionSequence ICS;
+    CheckReferenceInit(From, ToType, &ICS, SuppressUserConversions,
+                       /*AllowExplicit=*/false, ForceRValue);
+    return ICS;
+  } else {
+    return TryImplicitConversion(From, ToType, SuppressUserConversions,
+                                 ForceRValue);
+  }
+}
+
+/// PerformCopyInitialization - Copy-initialize an object of type @p ToType with
+/// the expression @p From. Returns true (and emits a diagnostic) if there was
+/// an error, returns false if the initialization succeeded. Elidable should
+/// be true when the copy may be elided (C++ 12.8p15). Overload resolution works
+/// differently in C++0x for this case.
+bool Sema::PerformCopyInitialization(Expr *&From, QualType ToType, 
+                                     const char* Flavor, bool Elidable) {
+  if (!getLangOptions().CPlusPlus) {
+    // In C, argument passing is the same as performing an assignment.
+    QualType FromType = From->getType();
+    
+    AssignConvertType ConvTy =
+      CheckSingleAssignmentConstraints(ToType, From);
+    if (ConvTy != Compatible &&
+        CheckTransparentUnionArgumentConstraints(ToType, From) == Compatible)
+      ConvTy = Compatible;
+    
+    return DiagnoseAssignmentResult(ConvTy, From->getLocStart(), ToType,
+                                    FromType, From, Flavor);
+  }
+
+  if (ToType->isReferenceType())
+    return CheckReferenceInit(From, ToType);
+
+  if (!PerformImplicitConversion(From, ToType, Flavor,
+                                 /*AllowExplicit=*/false, Elidable))
+    return false;
+
+  return Diag(From->getSourceRange().getBegin(),
+              diag::err_typecheck_convert_incompatible)
+    << ToType << From->getType() << Flavor << From->getSourceRange();
+}
+
+/// TryObjectArgumentInitialization - Try to initialize the object
+/// parameter of the given member function (@c Method) from the
+/// expression @p From.
+ImplicitConversionSequence
+Sema::TryObjectArgumentInitialization(Expr *From, CXXMethodDecl *Method) {
+  QualType ClassType = Context.getTypeDeclType(Method->getParent());
+  unsigned MethodQuals = Method->getTypeQualifiers();
+  QualType ImplicitParamType = ClassType.getQualifiedType(MethodQuals);
+
+  // Set up the conversion sequence as a "bad" conversion, to allow us
+  // to exit early.
+  ImplicitConversionSequence ICS;
+  ICS.Standard.setAsIdentityConversion();
+  ICS.ConversionKind = ImplicitConversionSequence::BadConversion;
+
+  // We need to have an object of class type.
+  QualType FromType = From->getType();
+  if (const PointerType *PT = FromType->getAsPointerType())
+    FromType = PT->getPointeeType();
+
+  assert(FromType->isRecordType());
+
+  // The implicit object parmeter is has the type "reference to cv X",
+  // where X is the class of which the function is a member
+  // (C++ [over.match.funcs]p4). However, when finding an implicit
+  // conversion sequence for the argument, we are not allowed to
+  // create temporaries or perform user-defined conversions 
+  // (C++ [over.match.funcs]p5). We perform a simplified version of
+  // reference binding here, that allows class rvalues to bind to
+  // non-constant references.
+
+  // First check the qualifiers. We don't care about lvalue-vs-rvalue
+  // with the implicit object parameter (C++ [over.match.funcs]p5).
+  QualType FromTypeCanon = Context.getCanonicalType(FromType);
+  if (ImplicitParamType.getCVRQualifiers() != FromType.getCVRQualifiers() &&
+      !ImplicitParamType.isAtLeastAsQualifiedAs(FromType))
+    return ICS;
+
+  // Check that we have either the same type or a derived type. It
+  // affects the conversion rank.
+  QualType ClassTypeCanon = Context.getCanonicalType(ClassType);
+  if (ClassTypeCanon == FromTypeCanon.getUnqualifiedType())
+    ICS.Standard.Second = ICK_Identity;
+  else if (IsDerivedFrom(FromType, ClassType))
+    ICS.Standard.Second = ICK_Derived_To_Base;
+  else
+    return ICS;
+
+  // Success. Mark this as a reference binding.
+  ICS.ConversionKind = ImplicitConversionSequence::StandardConversion;
+  ICS.Standard.FromTypePtr = FromType.getAsOpaquePtr();
+  ICS.Standard.ToTypePtr = ImplicitParamType.getAsOpaquePtr();
+  ICS.Standard.ReferenceBinding = true;
+  ICS.Standard.DirectBinding = true;
+  ICS.Standard.RRefBinding = false;
+  return ICS;
+}
+
+/// PerformObjectArgumentInitialization - Perform initialization of
+/// the implicit object parameter for the given Method with the given
+/// expression.
+bool
+Sema::PerformObjectArgumentInitialization(Expr *&From, CXXMethodDecl *Method) {
+  QualType FromRecordType, DestType;
+  QualType ImplicitParamRecordType  = 
+    Method->getThisType(Context)->getAsPointerType()->getPointeeType();
+  
+  if (const PointerType *PT = From->getType()->getAsPointerType()) {
+    FromRecordType = PT->getPointeeType();
+    DestType = Method->getThisType(Context);
+  } else {
+    FromRecordType = From->getType();
+    DestType = ImplicitParamRecordType;
+  }
+
+  ImplicitConversionSequence ICS 
+    = TryObjectArgumentInitialization(From, Method);
+  if (ICS.ConversionKind == ImplicitConversionSequence::BadConversion)
+    return Diag(From->getSourceRange().getBegin(),
+                diag::err_implicit_object_parameter_init)
+       << ImplicitParamRecordType << FromRecordType << From->getSourceRange();
+  
+  if (ICS.Standard.Second == ICK_Derived_To_Base &&
+      CheckDerivedToBaseConversion(FromRecordType,
+                                   ImplicitParamRecordType,
+                                   From->getSourceRange().getBegin(),
+                                   From->getSourceRange()))
+    return true;
+
+  ImpCastExprToType(From, DestType, /*isLvalue=*/true);
+  return false;
+}
+
+/// TryContextuallyConvertToBool - Attempt to contextually convert the
+/// expression From to bool (C++0x [conv]p3).
+ImplicitConversionSequence Sema::TryContextuallyConvertToBool(Expr *From) {
+  return TryImplicitConversion(From, Context.BoolTy, false, true);
+}
+
+/// PerformContextuallyConvertToBool - Perform a contextual conversion
+/// of the expression From to bool (C++0x [conv]p3).
+bool Sema::PerformContextuallyConvertToBool(Expr *&From) {
+  ImplicitConversionSequence ICS = TryContextuallyConvertToBool(From);
+  if (!PerformImplicitConversion(From, Context.BoolTy, ICS, "converting"))
+    return false;
+
+  return Diag(From->getSourceRange().getBegin(), 
+              diag::err_typecheck_bool_condition)
+    << From->getType() << From->getSourceRange();
+}
+
+/// AddOverloadCandidate - Adds the given function to the set of
+/// candidate functions, using the given function call arguments.  If
+/// @p SuppressUserConversions, then don't allow user-defined
+/// conversions via constructors or conversion operators.
+/// If @p ForceRValue, treat all arguments as rvalues. This is a slightly
+/// hacky way to implement the overloading rules for elidable copy
+/// initialization in C++0x (C++0x 12.8p15).
+void 
+Sema::AddOverloadCandidate(FunctionDecl *Function, 
+                           Expr **Args, unsigned NumArgs,
+                           OverloadCandidateSet& CandidateSet,
+                           bool SuppressUserConversions,
+                           bool ForceRValue)
+{
+  const FunctionProtoType* Proto 
+    = dyn_cast<FunctionProtoType>(Function->getType()->getAsFunctionType());
+  assert(Proto && "Functions without a prototype cannot be overloaded");
+  assert(!isa<CXXConversionDecl>(Function) && 
+         "Use AddConversionCandidate for conversion functions");
+
+  if (CXXMethodDecl *Method = dyn_cast<CXXMethodDecl>(Function)) {
+    if (!isa<CXXConstructorDecl>(Method)) {
+      // If we get here, it's because we're calling a member function
+      // that is named without a member access expression (e.g.,
+      // "this->f") that was either written explicitly or created
+      // implicitly. This can happen with a qualified call to a member
+      // function, e.g., X::f(). We use a NULL object as the implied
+      // object argument (C++ [over.call.func]p3).
+      AddMethodCandidate(Method, 0, Args, NumArgs, CandidateSet, 
+                         SuppressUserConversions, ForceRValue);
+      return;
+    }
+    // We treat a constructor like a non-member function, since its object
+    // argument doesn't participate in overload resolution.
+  }
+
+
+  // Add this candidate
+  CandidateSet.push_back(OverloadCandidate());
+  OverloadCandidate& Candidate = CandidateSet.back();
+  Candidate.Function = Function;
+  Candidate.Viable = true;
+  Candidate.IsSurrogate = false;
+  Candidate.IgnoreObjectArgument = false;
+
+  unsigned NumArgsInProto = Proto->getNumArgs();
+
+  // (C++ 13.3.2p2): A candidate function having fewer than m
+  // parameters is viable only if it has an ellipsis in its parameter
+  // list (8.3.5).
+  if (NumArgs > NumArgsInProto && !Proto->isVariadic()) {
+    Candidate.Viable = false;
+    return;
+  }
+
+  // (C++ 13.3.2p2): A candidate function having more than m parameters
+  // is viable only if the (m+1)st parameter has a default argument
+  // (8.3.6). For the purposes of overload resolution, the
+  // parameter list is truncated on the right, so that there are
+  // exactly m parameters.
+  unsigned MinRequiredArgs = Function->getMinRequiredArguments();
+  if (NumArgs < MinRequiredArgs) {
+    // Not enough arguments.
+    Candidate.Viable = false;
+    return;
+  }
+
+  // Determine the implicit conversion sequences for each of the
+  // arguments.
+  Candidate.Conversions.resize(NumArgs);
+  for (unsigned ArgIdx = 0; ArgIdx < NumArgs; ++ArgIdx) {
+    if (ArgIdx < NumArgsInProto) {
+      // (C++ 13.3.2p3): for F to be a viable function, there shall
+      // exist for each argument an implicit conversion sequence
+      // (13.3.3.1) that converts that argument to the corresponding
+      // parameter of F.
+      QualType ParamType = Proto->getArgType(ArgIdx);
+      Candidate.Conversions[ArgIdx] 
+        = TryCopyInitialization(Args[ArgIdx], ParamType, 
+                                SuppressUserConversions, ForceRValue);
+      if (Candidate.Conversions[ArgIdx].ConversionKind 
+            == ImplicitConversionSequence::BadConversion) {
+        Candidate.Viable = false;
+        break;
+      }
+    } else {
+      // (C++ 13.3.2p2): For the purposes of overload resolution, any
+      // argument for which there is no corresponding parameter is
+      // considered to ""match the ellipsis" (C+ 13.3.3.1.3).
+      Candidate.Conversions[ArgIdx].ConversionKind 
+        = ImplicitConversionSequence::EllipsisConversion;
+    }
+  }
+}
+
+/// \brief Add all of the function declarations in the given function set to
+/// the overload canddiate set.
+void Sema::AddFunctionCandidates(const FunctionSet &Functions,
+                                 Expr **Args, unsigned NumArgs,
+                                 OverloadCandidateSet& CandidateSet,
+                                 bool SuppressUserConversions) {
+  for (FunctionSet::const_iterator F = Functions.begin(), 
+                                FEnd = Functions.end();
+       F != FEnd; ++F)
+    AddOverloadCandidate(*F, Args, NumArgs, CandidateSet, 
+                         SuppressUserConversions);
+}
+
+/// AddMethodCandidate - Adds the given C++ member function to the set
+/// of candidate functions, using the given function call arguments
+/// and the object argument (@c Object). For example, in a call
+/// @c o.f(a1,a2), @c Object will contain @c o and @c Args will contain
+/// both @c a1 and @c a2. If @p SuppressUserConversions, then don't
+/// allow user-defined conversions via constructors or conversion
+/// operators. If @p ForceRValue, treat all arguments as rvalues. This is
+/// a slightly hacky way to implement the overloading rules for elidable copy
+/// initialization in C++0x (C++0x 12.8p15).
+void 
+Sema::AddMethodCandidate(CXXMethodDecl *Method, Expr *Object,
+                         Expr **Args, unsigned NumArgs,
+                         OverloadCandidateSet& CandidateSet,
+                         bool SuppressUserConversions, bool ForceRValue)
+{
+  const FunctionProtoType* Proto 
+    = dyn_cast<FunctionProtoType>(Method->getType()->getAsFunctionType());
+  assert(Proto && "Methods without a prototype cannot be overloaded");
+  assert(!isa<CXXConversionDecl>(Method) &&
+         "Use AddConversionCandidate for conversion functions");
+  assert(!isa<CXXConstructorDecl>(Method) &&
+         "Use AddOverloadCandidate for constructors");
+
+  // Add this candidate
+  CandidateSet.push_back(OverloadCandidate());
+  OverloadCandidate& Candidate = CandidateSet.back();
+  Candidate.Function = Method;
+  Candidate.IsSurrogate = false;
+  Candidate.IgnoreObjectArgument = false;
+
+  unsigned NumArgsInProto = Proto->getNumArgs();
+
+  // (C++ 13.3.2p2): A candidate function having fewer than m
+  // parameters is viable only if it has an ellipsis in its parameter
+  // list (8.3.5).
+  if (NumArgs > NumArgsInProto && !Proto->isVariadic()) {
+    Candidate.Viable = false;
+    return;
+  }
+
+  // (C++ 13.3.2p2): A candidate function having more than m parameters
+  // is viable only if the (m+1)st parameter has a default argument
+  // (8.3.6). For the purposes of overload resolution, the
+  // parameter list is truncated on the right, so that there are
+  // exactly m parameters.
+  unsigned MinRequiredArgs = Method->getMinRequiredArguments();
+  if (NumArgs < MinRequiredArgs) {
+    // Not enough arguments.
+    Candidate.Viable = false;
+    return;
+  }
+
+  Candidate.Viable = true;
+  Candidate.Conversions.resize(NumArgs + 1);
+
+  if (Method->isStatic() || !Object)
+    // The implicit object argument is ignored.
+    Candidate.IgnoreObjectArgument = true;
+  else {
+    // Determine the implicit conversion sequence for the object
+    // parameter.
+    Candidate.Conversions[0] = TryObjectArgumentInitialization(Object, Method);
+    if (Candidate.Conversions[0].ConversionKind 
+          == ImplicitConversionSequence::BadConversion) {
+      Candidate.Viable = false;
+      return;
+    }
+  }
+
+  // Determine the implicit conversion sequences for each of the
+  // arguments.
+  for (unsigned ArgIdx = 0; ArgIdx < NumArgs; ++ArgIdx) {
+    if (ArgIdx < NumArgsInProto) {
+      // (C++ 13.3.2p3): for F to be a viable function, there shall
+      // exist for each argument an implicit conversion sequence
+      // (13.3.3.1) that converts that argument to the corresponding
+      // parameter of F.
+      QualType ParamType = Proto->getArgType(ArgIdx);
+      Candidate.Conversions[ArgIdx + 1] 
+        = TryCopyInitialization(Args[ArgIdx], ParamType, 
+                                SuppressUserConversions, ForceRValue);
+      if (Candidate.Conversions[ArgIdx + 1].ConversionKind 
+            == ImplicitConversionSequence::BadConversion) {
+        Candidate.Viable = false;
+        break;
+      }
+    } else {
+      // (C++ 13.3.2p2): For the purposes of overload resolution, any
+      // argument for which there is no corresponding parameter is
+      // considered to ""match the ellipsis" (C+ 13.3.3.1.3).
+      Candidate.Conversions[ArgIdx + 1].ConversionKind 
+        = ImplicitConversionSequence::EllipsisConversion;
+    }
+  }
+}
+
+/// AddConversionCandidate - Add a C++ conversion function as a
+/// candidate in the candidate set (C++ [over.match.conv], 
+/// C++ [over.match.copy]). From is the expression we're converting from,
+/// and ToType is the type that we're eventually trying to convert to 
+/// (which may or may not be the same type as the type that the
+/// conversion function produces).
+void
+Sema::AddConversionCandidate(CXXConversionDecl *Conversion,
+                             Expr *From, QualType ToType,
+                             OverloadCandidateSet& CandidateSet) {
+  // Add this candidate
+  CandidateSet.push_back(OverloadCandidate());
+  OverloadCandidate& Candidate = CandidateSet.back();
+  Candidate.Function = Conversion;
+  Candidate.IsSurrogate = false;
+  Candidate.IgnoreObjectArgument = false;
+  Candidate.FinalConversion.setAsIdentityConversion();
+  Candidate.FinalConversion.FromTypePtr 
+    = Conversion->getConversionType().getAsOpaquePtr();
+  Candidate.FinalConversion.ToTypePtr = ToType.getAsOpaquePtr();
+
+  // Determine the implicit conversion sequence for the implicit
+  // object parameter.
+  Candidate.Viable = true;
+  Candidate.Conversions.resize(1);
+  Candidate.Conversions[0] = TryObjectArgumentInitialization(From, Conversion);
+
+  if (Candidate.Conversions[0].ConversionKind 
+      == ImplicitConversionSequence::BadConversion) {
+    Candidate.Viable = false;
+    return;
+  }
+
+  // To determine what the conversion from the result of calling the
+  // conversion function to the type we're eventually trying to
+  // convert to (ToType), we need to synthesize a call to the
+  // conversion function and attempt copy initialization from it. This
+  // makes sure that we get the right semantics with respect to
+  // lvalues/rvalues and the type. Fortunately, we can allocate this
+  // call on the stack and we don't need its arguments to be
+  // well-formed.
+  DeclRefExpr ConversionRef(Conversion, Conversion->getType(), 
+                            SourceLocation());
+  ImplicitCastExpr ConversionFn(Context.getPointerType(Conversion->getType()),
+                                &ConversionRef, false);
+  
+  // Note that it is safe to allocate CallExpr on the stack here because 
+  // there are 0 arguments (i.e., nothing is allocated using ASTContext's
+  // allocator).
+  CallExpr Call(Context, &ConversionFn, 0, 0, 
+                Conversion->getConversionType().getNonReferenceType(),
+                SourceLocation());
+  ImplicitConversionSequence ICS = TryCopyInitialization(&Call, ToType, true);
+  switch (ICS.ConversionKind) {
+  case ImplicitConversionSequence::StandardConversion:
+    Candidate.FinalConversion = ICS.Standard;
+    break;
+
+  case ImplicitConversionSequence::BadConversion:
+    Candidate.Viable = false;
+    break;
+
+  default:
+    assert(false && 
+           "Can only end up with a standard conversion sequence or failure");
+  }
+}
+
+/// AddSurrogateCandidate - Adds a "surrogate" candidate function that
+/// converts the given @c Object to a function pointer via the
+/// conversion function @c Conversion, and then attempts to call it
+/// with the given arguments (C++ [over.call.object]p2-4). Proto is
+/// the type of function that we'll eventually be calling.
+void Sema::AddSurrogateCandidate(CXXConversionDecl *Conversion,
+                                 const FunctionProtoType *Proto,
+                                 Expr *Object, Expr **Args, unsigned NumArgs,
+                                 OverloadCandidateSet& CandidateSet) {
+  CandidateSet.push_back(OverloadCandidate());
+  OverloadCandidate& Candidate = CandidateSet.back();
+  Candidate.Function = 0;
+  Candidate.Surrogate = Conversion;
+  Candidate.Viable = true;
+  Candidate.IsSurrogate = true;
+  Candidate.IgnoreObjectArgument = false;
+  Candidate.Conversions.resize(NumArgs + 1);
+
+  // Determine the implicit conversion sequence for the implicit
+  // object parameter.
+  ImplicitConversionSequence ObjectInit 
+    = TryObjectArgumentInitialization(Object, Conversion);
+  if (ObjectInit.ConversionKind == ImplicitConversionSequence::BadConversion) {
+    Candidate.Viable = false;
+    return;
+  }
+
+  // The first conversion is actually a user-defined conversion whose
+  // first conversion is ObjectInit's standard conversion (which is
+  // effectively a reference binding). Record it as such.
+  Candidate.Conversions[0].ConversionKind 
+    = ImplicitConversionSequence::UserDefinedConversion;
+  Candidate.Conversions[0].UserDefined.Before = ObjectInit.Standard;
+  Candidate.Conversions[0].UserDefined.ConversionFunction = Conversion;
+  Candidate.Conversions[0].UserDefined.After 
+    = Candidate.Conversions[0].UserDefined.Before;
+  Candidate.Conversions[0].UserDefined.After.setAsIdentityConversion();
+
+  // Find the 
+  unsigned NumArgsInProto = Proto->getNumArgs();
+
+  // (C++ 13.3.2p2): A candidate function having fewer than m
+  // parameters is viable only if it has an ellipsis in its parameter
+  // list (8.3.5).
+  if (NumArgs > NumArgsInProto && !Proto->isVariadic()) {
+    Candidate.Viable = false;
+    return;
+  }
+
+  // Function types don't have any default arguments, so just check if
+  // we have enough arguments.
+  if (NumArgs < NumArgsInProto) {
+    // Not enough arguments.
+    Candidate.Viable = false;
+    return;
+  }
+
+  // Determine the implicit conversion sequences for each of the
+  // arguments.
+  for (unsigned ArgIdx = 0; ArgIdx < NumArgs; ++ArgIdx) {
+    if (ArgIdx < NumArgsInProto) {
+      // (C++ 13.3.2p3): for F to be a viable function, there shall
+      // exist for each argument an implicit conversion sequence
+      // (13.3.3.1) that converts that argument to the corresponding
+      // parameter of F.
+      QualType ParamType = Proto->getArgType(ArgIdx);
+      Candidate.Conversions[ArgIdx + 1] 
+        = TryCopyInitialization(Args[ArgIdx], ParamType, 
+                                /*SuppressUserConversions=*/false);
+      if (Candidate.Conversions[ArgIdx + 1].ConversionKind 
+            == ImplicitConversionSequence::BadConversion) {
+        Candidate.Viable = false;
+        break;
+      }
+    } else {
+      // (C++ 13.3.2p2): For the purposes of overload resolution, any
+      // argument for which there is no corresponding parameter is
+      // considered to ""match the ellipsis" (C+ 13.3.3.1.3).
+      Candidate.Conversions[ArgIdx + 1].ConversionKind 
+        = ImplicitConversionSequence::EllipsisConversion;
+    }
+  }
+}
+
+// FIXME: This will eventually be removed, once we've migrated all of the
+// operator overloading logic over to the scheme used by binary operators, which
+// works for template instantiation.
+void Sema::AddOperatorCandidates(OverloadedOperatorKind Op, Scope *S,
+                                 SourceLocation OpLoc,
+                                 Expr **Args, unsigned NumArgs,
+                                 OverloadCandidateSet& CandidateSet,
+                                 SourceRange OpRange) {
+
+  FunctionSet Functions;
+
+  QualType T1 = Args[0]->getType();
+  QualType T2;
+  if (NumArgs > 1)
+    T2 = Args[1]->getType();
+
+  DeclarationName OpName = Context.DeclarationNames.getCXXOperatorName(Op);
+  if (S)
+    LookupOverloadedOperatorName(Op, S, T1, T2, Functions);
+  ArgumentDependentLookup(OpName, Args, NumArgs, Functions);
+  AddFunctionCandidates(Functions, Args, NumArgs, CandidateSet);
+  AddMemberOperatorCandidates(Op, OpLoc, Args, NumArgs, CandidateSet, OpRange);
+  AddBuiltinOperatorCandidates(Op, Args, NumArgs, CandidateSet);
+}
+
+/// \brief Add overload candidates for overloaded operators that are
+/// member functions.
+///
+/// Add the overloaded operator candidates that are member functions
+/// for the operator Op that was used in an operator expression such
+/// as "x Op y". , Args/NumArgs provides the operator arguments, and
+/// CandidateSet will store the added overload candidates. (C++
+/// [over.match.oper]).
+void Sema::AddMemberOperatorCandidates(OverloadedOperatorKind Op,
+                                       SourceLocation OpLoc,
+                                       Expr **Args, unsigned NumArgs,
+                                       OverloadCandidateSet& CandidateSet,
+                                       SourceRange OpRange) {
+  DeclarationName OpName = Context.DeclarationNames.getCXXOperatorName(Op);
+
+  // C++ [over.match.oper]p3:
+  //   For a unary operator @ with an operand of a type whose
+  //   cv-unqualified version is T1, and for a binary operator @ with
+  //   a left operand of a type whose cv-unqualified version is T1 and
+  //   a right operand of a type whose cv-unqualified version is T2,
+  //   three sets of candidate functions, designated member
+  //   candidates, non-member candidates and built-in candidates, are
+  //   constructed as follows:
+  QualType T1 = Args[0]->getType();
+  QualType T2;
+  if (NumArgs > 1)
+    T2 = Args[1]->getType();
+
+  //     -- If T1 is a class type, the set of member candidates is the
+  //        result of the qualified lookup of T1::operator@
+  //        (13.3.1.1.1); otherwise, the set of member candidates is
+  //        empty.
+  // FIXME: Lookup in base classes, too!
+  if (const RecordType *T1Rec = T1->getAsRecordType()) {
+    DeclContext::lookup_const_iterator Oper, OperEnd;
+    for (llvm::tie(Oper, OperEnd) = T1Rec->getDecl()->lookup(Context, OpName);
+         Oper != OperEnd; ++Oper)
+      AddMethodCandidate(cast<CXXMethodDecl>(*Oper), Args[0], 
+                         Args+1, NumArgs - 1, CandidateSet,
+                         /*SuppressUserConversions=*/false);
+  }
+}
+
+/// AddBuiltinCandidate - Add a candidate for a built-in
+/// operator. ResultTy and ParamTys are the result and parameter types
+/// of the built-in candidate, respectively. Args and NumArgs are the
+/// arguments being passed to the candidate. IsAssignmentOperator
+/// should be true when this built-in candidate is an assignment
+/// operator. NumContextualBoolArguments is the number of arguments
+/// (at the beginning of the argument list) that will be contextually
+/// converted to bool.
+void Sema::AddBuiltinCandidate(QualType ResultTy, QualType *ParamTys, 
+                               Expr **Args, unsigned NumArgs,
+                               OverloadCandidateSet& CandidateSet,
+                               bool IsAssignmentOperator,
+                               unsigned NumContextualBoolArguments) {
+  // Add this candidate
+  CandidateSet.push_back(OverloadCandidate());
+  OverloadCandidate& Candidate = CandidateSet.back();
+  Candidate.Function = 0;
+  Candidate.IsSurrogate = false;
+  Candidate.IgnoreObjectArgument = false;
+  Candidate.BuiltinTypes.ResultTy = ResultTy;
+  for (unsigned ArgIdx = 0; ArgIdx < NumArgs; ++ArgIdx)
+    Candidate.BuiltinTypes.ParamTypes[ArgIdx] = ParamTys[ArgIdx];
+
+  // Determine the implicit conversion sequences for each of the
+  // arguments.
+  Candidate.Viable = true;
+  Candidate.Conversions.resize(NumArgs);
+  for (unsigned ArgIdx = 0; ArgIdx < NumArgs; ++ArgIdx) {
+    // C++ [over.match.oper]p4:
+    //   For the built-in assignment operators, conversions of the
+    //   left operand are restricted as follows:
+    //     -- no temporaries are introduced to hold the left operand, and
+    //     -- no user-defined conversions are applied to the left
+    //        operand to achieve a type match with the left-most
+    //        parameter of a built-in candidate. 
+    //
+    // We block these conversions by turning off user-defined
+    // conversions, since that is the only way that initialization of
+    // a reference to a non-class type can occur from something that
+    // is not of the same type.
+    if (ArgIdx < NumContextualBoolArguments) {
+      assert(ParamTys[ArgIdx] == Context.BoolTy && 
+             "Contextual conversion to bool requires bool type");
+      Candidate.Conversions[ArgIdx] = TryContextuallyConvertToBool(Args[ArgIdx]);
+    } else {
+      Candidate.Conversions[ArgIdx] 
+        = TryCopyInitialization(Args[ArgIdx], ParamTys[ArgIdx], 
+                                ArgIdx == 0 && IsAssignmentOperator);
+    }
+    if (Candidate.Conversions[ArgIdx].ConversionKind 
+        == ImplicitConversionSequence::BadConversion) {
+      Candidate.Viable = false;
+      break;
+    }
+  }
+}
+
+/// BuiltinCandidateTypeSet - A set of types that will be used for the
+/// candidate operator functions for built-in operators (C++
+/// [over.built]). The types are separated into pointer types and
+/// enumeration types.
+class BuiltinCandidateTypeSet  {
+  /// TypeSet - A set of types.
+  typedef llvm::SmallPtrSet<QualType, 8> TypeSet;
+
+  /// PointerTypes - The set of pointer types that will be used in the
+  /// built-in candidates.
+  TypeSet PointerTypes;
+
+  /// MemberPointerTypes - The set of member pointer types that will be
+  /// used in the built-in candidates.
+  TypeSet MemberPointerTypes;
+
+  /// EnumerationTypes - The set of enumeration types that will be
+  /// used in the built-in candidates.
+  TypeSet EnumerationTypes;
+
+  /// Context - The AST context in which we will build the type sets.
+  ASTContext &Context;
+
+  bool AddPointerWithMoreQualifiedTypeVariants(QualType Ty);
+  bool AddMemberPointerWithMoreQualifiedTypeVariants(QualType Ty);
+
+public:
+  /// iterator - Iterates through the types that are part of the set.
+  typedef TypeSet::iterator iterator;
+
+  BuiltinCandidateTypeSet(ASTContext &Context) : Context(Context) { }
+
+  void AddTypesConvertedFrom(QualType Ty, bool AllowUserConversions,
+                             bool AllowExplicitConversions);
+
+  /// pointer_begin - First pointer type found;
+  iterator pointer_begin() { return PointerTypes.begin(); }
+
+  /// pointer_end - Past the last pointer type found;
+  iterator pointer_end() { return PointerTypes.end(); }
+
+  /// member_pointer_begin - First member pointer type found;
+  iterator member_pointer_begin() { return MemberPointerTypes.begin(); }
+
+  /// member_pointer_end - Past the last member pointer type found;
+  iterator member_pointer_end() { return MemberPointerTypes.end(); }
+
+  /// enumeration_begin - First enumeration type found;
+  iterator enumeration_begin() { return EnumerationTypes.begin(); }
+
+  /// enumeration_end - Past the last enumeration type found;
+  iterator enumeration_end() { return EnumerationTypes.end(); }
+};
+
+/// AddPointerWithMoreQualifiedTypeVariants - Add the pointer type @p Ty to
+/// the set of pointer types along with any more-qualified variants of
+/// that type. For example, if @p Ty is "int const *", this routine
+/// will add "int const *", "int const volatile *", "int const
+/// restrict *", and "int const volatile restrict *" to the set of
+/// pointer types. Returns true if the add of @p Ty itself succeeded,
+/// false otherwise.
+bool
+BuiltinCandidateTypeSet::AddPointerWithMoreQualifiedTypeVariants(QualType Ty) {
+  // Insert this type.
+  if (!PointerTypes.insert(Ty))
+    return false;
+
+  if (const PointerType *PointerTy = Ty->getAsPointerType()) {
+    QualType PointeeTy = PointerTy->getPointeeType();
+    // FIXME: Optimize this so that we don't keep trying to add the same types.
+
+    // FIXME: Do we have to add CVR qualifiers at *all* levels to deal with all
+    // pointer conversions that don't cast away constness?
+    if (!PointeeTy.isConstQualified())
+      AddPointerWithMoreQualifiedTypeVariants
+        (Context.getPointerType(PointeeTy.withConst()));
+    if (!PointeeTy.isVolatileQualified())
+      AddPointerWithMoreQualifiedTypeVariants
+        (Context.getPointerType(PointeeTy.withVolatile()));
+    if (!PointeeTy.isRestrictQualified())
+      AddPointerWithMoreQualifiedTypeVariants
+        (Context.getPointerType(PointeeTy.withRestrict()));
+  }
+
+  return true;
+}
+
+/// AddMemberPointerWithMoreQualifiedTypeVariants - Add the pointer type @p Ty
+/// to the set of pointer types along with any more-qualified variants of
+/// that type. For example, if @p Ty is "int const *", this routine
+/// will add "int const *", "int const volatile *", "int const
+/// restrict *", and "int const volatile restrict *" to the set of
+/// pointer types. Returns true if the add of @p Ty itself succeeded,
+/// false otherwise.
+bool
+BuiltinCandidateTypeSet::AddMemberPointerWithMoreQualifiedTypeVariants(
+    QualType Ty) {
+  // Insert this type.
+  if (!MemberPointerTypes.insert(Ty))
+    return false;
+
+  if (const MemberPointerType *PointerTy = Ty->getAsMemberPointerType()) {
+    QualType PointeeTy = PointerTy->getPointeeType();
+    const Type *ClassTy = PointerTy->getClass();
+    // FIXME: Optimize this so that we don't keep trying to add the same types.
+
+    if (!PointeeTy.isConstQualified())
+      AddMemberPointerWithMoreQualifiedTypeVariants
+        (Context.getMemberPointerType(PointeeTy.withConst(), ClassTy));
+    if (!PointeeTy.isVolatileQualified())
+      AddMemberPointerWithMoreQualifiedTypeVariants
+        (Context.getMemberPointerType(PointeeTy.withVolatile(), ClassTy));
+    if (!PointeeTy.isRestrictQualified())
+      AddMemberPointerWithMoreQualifiedTypeVariants
+        (Context.getMemberPointerType(PointeeTy.withRestrict(), ClassTy));
+  }
+
+  return true;
+}
+
+/// AddTypesConvertedFrom - Add each of the types to which the type @p
+/// Ty can be implicit converted to the given set of @p Types. We're
+/// primarily interested in pointer types and enumeration types. We also
+/// take member pointer types, for the conditional operator.
+/// AllowUserConversions is true if we should look at the conversion
+/// functions of a class type, and AllowExplicitConversions if we
+/// should also include the explicit conversion functions of a class
+/// type.
+void 
+BuiltinCandidateTypeSet::AddTypesConvertedFrom(QualType Ty,
+                                               bool AllowUserConversions,
+                                               bool AllowExplicitConversions) {
+  // Only deal with canonical types.
+  Ty = Context.getCanonicalType(Ty);
+
+  // Look through reference types; they aren't part of the type of an
+  // expression for the purposes of conversions.
+  if (const ReferenceType *RefTy = Ty->getAsReferenceType())
+    Ty = RefTy->getPointeeType();
+
+  // We don't care about qualifiers on the type.
+  Ty = Ty.getUnqualifiedType();
+
+  if (const PointerType *PointerTy = Ty->getAsPointerType()) {
+    QualType PointeeTy = PointerTy->getPointeeType();
+
+    // Insert our type, and its more-qualified variants, into the set
+    // of types.
+    if (!AddPointerWithMoreQualifiedTypeVariants(Ty))
+      return;
+
+    // Add 'cv void*' to our set of types.
+    if (!Ty->isVoidType()) {
+      QualType QualVoid 
+        = Context.VoidTy.getQualifiedType(PointeeTy.getCVRQualifiers());
+      AddPointerWithMoreQualifiedTypeVariants(Context.getPointerType(QualVoid));
+    }
+
+    // If this is a pointer to a class type, add pointers to its bases
+    // (with the same level of cv-qualification as the original
+    // derived class, of course).
+    if (const RecordType *PointeeRec = PointeeTy->getAsRecordType()) {
+      CXXRecordDecl *ClassDecl = cast<CXXRecordDecl>(PointeeRec->getDecl());
+      for (CXXRecordDecl::base_class_iterator Base = ClassDecl->bases_begin();
+           Base != ClassDecl->bases_end(); ++Base) {
+        QualType BaseTy = Context.getCanonicalType(Base->getType());
+        BaseTy = BaseTy.getQualifiedType(PointeeTy.getCVRQualifiers());
+
+        // Add the pointer type, recursively, so that we get all of
+        // the indirect base classes, too.
+        AddTypesConvertedFrom(Context.getPointerType(BaseTy), false, false);
+      }
+    }
+  } else if (Ty->isMemberPointerType()) {
+    // Member pointers are far easier, since the pointee can't be converted.
+    if (!AddMemberPointerWithMoreQualifiedTypeVariants(Ty))
+      return;
+  } else if (Ty->isEnumeralType()) {
+    EnumerationTypes.insert(Ty);
+  } else if (AllowUserConversions) {
+    if (const RecordType *TyRec = Ty->getAsRecordType()) {
+      CXXRecordDecl *ClassDecl = cast<CXXRecordDecl>(TyRec->getDecl());
+      // FIXME: Visit conversion functions in the base classes, too.
+      OverloadedFunctionDecl *Conversions 
+        = ClassDecl->getConversionFunctions();
+      for (OverloadedFunctionDecl::function_iterator Func 
+             = Conversions->function_begin();
+           Func != Conversions->function_end(); ++Func) {
+        CXXConversionDecl *Conv = cast<CXXConversionDecl>(*Func);
+        if (AllowExplicitConversions || !Conv->isExplicit())
+          AddTypesConvertedFrom(Conv->getConversionType(), false, false);
+      }
+    }
+  }
+}
+
+/// AddBuiltinOperatorCandidates - Add the appropriate built-in
+/// operator overloads to the candidate set (C++ [over.built]), based
+/// on the operator @p Op and the arguments given. For example, if the
+/// operator is a binary '+', this routine might add "int
+/// operator+(int, int)" to cover integer addition.
+void
+Sema::AddBuiltinOperatorCandidates(OverloadedOperatorKind Op, 
+                                   Expr **Args, unsigned NumArgs,
+                                   OverloadCandidateSet& CandidateSet) {
+  // The set of "promoted arithmetic types", which are the arithmetic
+  // types are that preserved by promotion (C++ [over.built]p2). Note
+  // that the first few of these types are the promoted integral
+  // types; these types need to be first.
+  // FIXME: What about complex?
+  const unsigned FirstIntegralType = 0;
+  const unsigned LastIntegralType = 13;
+  const unsigned FirstPromotedIntegralType = 7, 
+                 LastPromotedIntegralType = 13;
+  const unsigned FirstPromotedArithmeticType = 7,
+                 LastPromotedArithmeticType = 16;
+  const unsigned NumArithmeticTypes = 16;
+  QualType ArithmeticTypes[NumArithmeticTypes] = {
+    Context.BoolTy, Context.CharTy, Context.WCharTy,
+    Context.SignedCharTy, Context.ShortTy,
+    Context.UnsignedCharTy, Context.UnsignedShortTy,
+    Context.IntTy, Context.LongTy, Context.LongLongTy,
+    Context.UnsignedIntTy, Context.UnsignedLongTy, Context.UnsignedLongLongTy,
+    Context.FloatTy, Context.DoubleTy, Context.LongDoubleTy
+  };
+
+  // Find all of the types that the arguments can convert to, but only
+  // if the operator we're looking at has built-in operator candidates
+  // that make use of these types.
+  BuiltinCandidateTypeSet CandidateTypes(Context);
+  if (Op == OO_Less || Op == OO_Greater || Op == OO_LessEqual ||
+      Op == OO_GreaterEqual || Op == OO_EqualEqual || Op == OO_ExclaimEqual ||
+      Op == OO_Plus || (Op == OO_Minus && NumArgs == 2) || Op == OO_Equal ||
+      Op == OO_PlusEqual || Op == OO_MinusEqual || Op == OO_Subscript ||
+      Op == OO_ArrowStar || Op == OO_PlusPlus || Op == OO_MinusMinus ||
+      (Op == OO_Star && NumArgs == 1) || Op == OO_Conditional) {
+    for (unsigned ArgIdx = 0; ArgIdx < NumArgs; ++ArgIdx)
+      CandidateTypes.AddTypesConvertedFrom(Args[ArgIdx]->getType(),
+                                           true,
+                                           (Op == OO_Exclaim ||
+                                            Op == OO_AmpAmp ||
+                                            Op == OO_PipePipe));
+  }
+
+  bool isComparison = false;
+  switch (Op) {
+  case OO_None:
+  case NUM_OVERLOADED_OPERATORS:
+    assert(false && "Expected an overloaded operator");
+    break;
+
+  case OO_Star: // '*' is either unary or binary
+    if (NumArgs == 1) 
+      goto UnaryStar;
+    else
+      goto BinaryStar;
+    break;
+
+  case OO_Plus: // '+' is either unary or binary
+    if (NumArgs == 1)
+      goto UnaryPlus;
+    else
+      goto BinaryPlus;
+    break;
+
+  case OO_Minus: // '-' is either unary or binary
+    if (NumArgs == 1)
+      goto UnaryMinus;
+    else
+      goto BinaryMinus;
+    break;
+
+  case OO_Amp: // '&' is either unary or binary
+    if (NumArgs == 1)
+      goto UnaryAmp;
+    else
+      goto BinaryAmp;
+
+  case OO_PlusPlus:
+  case OO_MinusMinus:
+    // C++ [over.built]p3:
+    //
+    //   For every pair (T, VQ), where T is an arithmetic type, and VQ
+    //   is either volatile or empty, there exist candidate operator
+    //   functions of the form
+    //
+    //       VQ T&      operator++(VQ T&);
+    //       T          operator++(VQ T&, int);
+    //
+    // C++ [over.built]p4:
+    //
+    //   For every pair (T, VQ), where T is an arithmetic type other
+    //   than bool, and VQ is either volatile or empty, there exist
+    //   candidate operator functions of the form
+    //
+    //       VQ T&      operator--(VQ T&);
+    //       T          operator--(VQ T&, int);
+    for (unsigned Arith = (Op == OO_PlusPlus? 0 : 1); 
+         Arith < NumArithmeticTypes; ++Arith) {
+      QualType ArithTy = ArithmeticTypes[Arith];
+      QualType ParamTypes[2] 
+        = { Context.getLValueReferenceType(ArithTy), Context.IntTy };
+
+      // Non-volatile version.
+      if (NumArgs == 1)
+        AddBuiltinCandidate(ParamTypes[0], ParamTypes, Args, 1, CandidateSet);
+      else
+        AddBuiltinCandidate(ArithTy, ParamTypes, Args, 2, CandidateSet);
+
+      // Volatile version
+      ParamTypes[0] = Context.getLValueReferenceType(ArithTy.withVolatile());
+      if (NumArgs == 1)
+        AddBuiltinCandidate(ParamTypes[0], ParamTypes, Args, 1, CandidateSet);
+      else
+        AddBuiltinCandidate(ArithTy, ParamTypes, Args, 2, CandidateSet);
+    }
+
+    // C++ [over.built]p5:
+    //
+    //   For every pair (T, VQ), where T is a cv-qualified or
+    //   cv-unqualified object type, and VQ is either volatile or
+    //   empty, there exist candidate operator functions of the form
+    //
+    //       T*VQ&      operator++(T*VQ&);
+    //       T*VQ&      operator--(T*VQ&);
+    //       T*         operator++(T*VQ&, int);
+    //       T*         operator--(T*VQ&, int);
+    for (BuiltinCandidateTypeSet::iterator Ptr = CandidateTypes.pointer_begin();
+         Ptr != CandidateTypes.pointer_end(); ++Ptr) {
+      // Skip pointer types that aren't pointers to object types.
+      if (!(*Ptr)->getAsPointerType()->getPointeeType()->isObjectType())
+        continue;
+
+      QualType ParamTypes[2] = { 
+        Context.getLValueReferenceType(*Ptr), Context.IntTy 
+      };
+      
+      // Without volatile
+      if (NumArgs == 1)
+        AddBuiltinCandidate(ParamTypes[0], ParamTypes, Args, 1, CandidateSet);
+      else
+        AddBuiltinCandidate(*Ptr, ParamTypes, Args, 2, CandidateSet);
+
+      if (!Context.getCanonicalType(*Ptr).isVolatileQualified()) {
+        // With volatile
+        ParamTypes[0] = Context.getLValueReferenceType((*Ptr).withVolatile());
+        if (NumArgs == 1)
+          AddBuiltinCandidate(ParamTypes[0], ParamTypes, Args, 1, CandidateSet);
+        else
+          AddBuiltinCandidate(*Ptr, ParamTypes, Args, 2, CandidateSet);
+      }
+    }
+    break;
+
+  UnaryStar:
+    // C++ [over.built]p6:
+    //   For every cv-qualified or cv-unqualified object type T, there
+    //   exist candidate operator functions of the form
+    //
+    //       T&         operator*(T*);
+    //
+    // C++ [over.built]p7:
+    //   For every function type T, there exist candidate operator
+    //   functions of the form
+    //       T&         operator*(T*);
+    for (BuiltinCandidateTypeSet::iterator Ptr = CandidateTypes.pointer_begin();
+         Ptr != CandidateTypes.pointer_end(); ++Ptr) {
+      QualType ParamTy = *Ptr;
+      QualType PointeeTy = ParamTy->getAsPointerType()->getPointeeType();
+      AddBuiltinCandidate(Context.getLValueReferenceType(PointeeTy), 
+                          &ParamTy, Args, 1, CandidateSet);
+    }
+    break;
+
+  UnaryPlus:
+    // C++ [over.built]p8:
+    //   For every type T, there exist candidate operator functions of
+    //   the form
+    //
+    //       T*         operator+(T*);
+    for (BuiltinCandidateTypeSet::iterator Ptr = CandidateTypes.pointer_begin();
+         Ptr != CandidateTypes.pointer_end(); ++Ptr) {
+      QualType ParamTy = *Ptr;
+      AddBuiltinCandidate(ParamTy, &ParamTy, Args, 1, CandidateSet);
+    }
+    
+    // Fall through
+
+  UnaryMinus:
+    // C++ [over.built]p9:
+    //  For every promoted arithmetic type T, there exist candidate
+    //  operator functions of the form
+    //
+    //       T         operator+(T);
+    //       T         operator-(T);
+    for (unsigned Arith = FirstPromotedArithmeticType; 
+         Arith < LastPromotedArithmeticType; ++Arith) {
+      QualType ArithTy = ArithmeticTypes[Arith];
+      AddBuiltinCandidate(ArithTy, &ArithTy, Args, 1, CandidateSet);
+    }
+    break;
+
+  case OO_Tilde:
+    // C++ [over.built]p10:
+    //   For every promoted integral type T, there exist candidate
+    //   operator functions of the form
+    //
+    //        T         operator~(T);
+    for (unsigned Int = FirstPromotedIntegralType; 
+         Int < LastPromotedIntegralType; ++Int) {
+      QualType IntTy = ArithmeticTypes[Int];
+      AddBuiltinCandidate(IntTy, &IntTy, Args, 1, CandidateSet);
+    }
+    break;
+
+  case OO_New:
+  case OO_Delete:
+  case OO_Array_New:
+  case OO_Array_Delete:
+  case OO_Call:
+    assert(false && "Special operators don't use AddBuiltinOperatorCandidates");
+    break;
+
+  case OO_Comma:
+  UnaryAmp:
+  case OO_Arrow:
+    // C++ [over.match.oper]p3:
+    //   -- For the operator ',', the unary operator '&', or the
+    //      operator '->', the built-in candidates set is empty.
+    break;
+
+  case OO_Less:
+  case OO_Greater:
+  case OO_LessEqual:
+  case OO_GreaterEqual:
+  case OO_EqualEqual:
+  case OO_ExclaimEqual:
+    // C++ [over.built]p15:
+    //
+    //   For every pointer or enumeration type T, there exist
+    //   candidate operator functions of the form
+    //     
+    //        bool       operator<(T, T);
+    //        bool       operator>(T, T);
+    //        bool       operator<=(T, T);
+    //        bool       operator>=(T, T);
+    //        bool       operator==(T, T);
+    //        bool       operator!=(T, T);
+    for (BuiltinCandidateTypeSet::iterator Ptr = CandidateTypes.pointer_begin();
+         Ptr != CandidateTypes.pointer_end(); ++Ptr) {
+      QualType ParamTypes[2] = { *Ptr, *Ptr };
+      AddBuiltinCandidate(Context.BoolTy, ParamTypes, Args, 2, CandidateSet);
+    }
+    for (BuiltinCandidateTypeSet::iterator Enum 
+           = CandidateTypes.enumeration_begin();
+         Enum != CandidateTypes.enumeration_end(); ++Enum) {
+      QualType ParamTypes[2] = { *Enum, *Enum };
+      AddBuiltinCandidate(Context.BoolTy, ParamTypes, Args, 2, CandidateSet);
+    }
+
+    // Fall through.
+    isComparison = true;
+
+  BinaryPlus:
+  BinaryMinus:
+    if (!isComparison) {
+      // We didn't fall through, so we must have OO_Plus or OO_Minus.
+
+      // C++ [over.built]p13:
+      //
+      //   For every cv-qualified or cv-unqualified object type T
+      //   there exist candidate operator functions of the form
+      //    
+      //      T*         operator+(T*, ptrdiff_t);
+      //      T&         operator[](T*, ptrdiff_t);    [BELOW]
+      //      T*         operator-(T*, ptrdiff_t);
+      //      T*         operator+(ptrdiff_t, T*);
+      //      T&         operator[](ptrdiff_t, T*);    [BELOW]
+      //
+      // C++ [over.built]p14:
+      //
+      //   For every T, where T is a pointer to object type, there
+      //   exist candidate operator functions of the form
+      //
+      //      ptrdiff_t  operator-(T, T);
+      for (BuiltinCandidateTypeSet::iterator Ptr 
+             = CandidateTypes.pointer_begin();
+           Ptr != CandidateTypes.pointer_end(); ++Ptr) {
+        QualType ParamTypes[2] = { *Ptr, Context.getPointerDiffType() };
+
+        // operator+(T*, ptrdiff_t) or operator-(T*, ptrdiff_t)
+        AddBuiltinCandidate(*Ptr, ParamTypes, Args, 2, CandidateSet);
+
+        if (Op == OO_Plus) {
+          // T* operator+(ptrdiff_t, T*);
+          ParamTypes[0] = ParamTypes[1];
+          ParamTypes[1] = *Ptr;
+          AddBuiltinCandidate(*Ptr, ParamTypes, Args, 2, CandidateSet);
+        } else {
+          // ptrdiff_t operator-(T, T);
+          ParamTypes[1] = *Ptr;
+          AddBuiltinCandidate(Context.getPointerDiffType(), ParamTypes,
+                              Args, 2, CandidateSet);
+        }
+      }
+    }
+    // Fall through
+
+  case OO_Slash:
+  BinaryStar:
+  Conditional:
+    // C++ [over.built]p12:
+    //
+    //   For every pair of promoted arithmetic types L and R, there
+    //   exist candidate operator functions of the form
+    //
+    //        LR         operator*(L, R);
+    //        LR         operator/(L, R);
+    //        LR         operator+(L, R);
+    //        LR         operator-(L, R);
+    //        bool       operator<(L, R);
+    //        bool       operator>(L, R);
+    //        bool       operator<=(L, R);
+    //        bool       operator>=(L, R);
+    //        bool       operator==(L, R);
+    //        bool       operator!=(L, R);
+    //
+    //   where LR is the result of the usual arithmetic conversions
+    //   between types L and R.
+    //
+    // C++ [over.built]p24:
+    //
+    //   For every pair of promoted arithmetic types L and R, there exist
+    //   candidate operator functions of the form
+    //
+    //        LR       operator?(bool, L, R);
+    //
+    //   where LR is the result of the usual arithmetic conversions
+    //   between types L and R.
+    // Our candidates ignore the first parameter.
+    for (unsigned Left = FirstPromotedArithmeticType; 
+         Left < LastPromotedArithmeticType; ++Left) {
+      for (unsigned Right = FirstPromotedArithmeticType; 
+           Right < LastPromotedArithmeticType; ++Right) {
+        QualType LandR[2] = { ArithmeticTypes[Left], ArithmeticTypes[Right] };
+        QualType Result 
+          = isComparison? Context.BoolTy 
+                        : UsualArithmeticConversionsType(LandR[0], LandR[1]);
+        AddBuiltinCandidate(Result, LandR, Args, 2, CandidateSet);
+      }
+    }
+    break;
+
+  case OO_Percent:
+  BinaryAmp:
+  case OO_Caret:
+  case OO_Pipe:
+  case OO_LessLess:
+  case OO_GreaterGreater:
+    // C++ [over.built]p17:
+    //
+    //   For every pair of promoted integral types L and R, there
+    //   exist candidate operator functions of the form
+    //
+    //      LR         operator%(L, R);
+    //      LR         operator&(L, R);
+    //      LR         operator^(L, R);
+    //      LR         operator|(L, R);
+    //      L          operator<<(L, R);
+    //      L          operator>>(L, R);
+    //
+    //   where LR is the result of the usual arithmetic conversions
+    //   between types L and R.
+    for (unsigned Left = FirstPromotedIntegralType; 
+         Left < LastPromotedIntegralType; ++Left) {
+      for (unsigned Right = FirstPromotedIntegralType; 
+           Right < LastPromotedIntegralType; ++Right) {
+        QualType LandR[2] = { ArithmeticTypes[Left], ArithmeticTypes[Right] };
+        QualType Result = (Op == OO_LessLess || Op == OO_GreaterGreater)
+            ? LandR[0]
+            : UsualArithmeticConversionsType(LandR[0], LandR[1]);
+        AddBuiltinCandidate(Result, LandR, Args, 2, CandidateSet);
+      }
+    }
+    break;
+
+  case OO_Equal:
+    // C++ [over.built]p20:
+    //
+    //   For every pair (T, VQ), where T is an enumeration or
+    //   (FIXME:) pointer to member type and VQ is either volatile or
+    //   empty, there exist candidate operator functions of the form
+    //
+    //        VQ T&      operator=(VQ T&, T);
+    for (BuiltinCandidateTypeSet::iterator Enum 
+           = CandidateTypes.enumeration_begin();
+         Enum != CandidateTypes.enumeration_end(); ++Enum) {
+      QualType ParamTypes[2];
+
+      // T& operator=(T&, T)
+      ParamTypes[0] = Context.getLValueReferenceType(*Enum);
+      ParamTypes[1] = *Enum;
+      AddBuiltinCandidate(ParamTypes[0], ParamTypes, Args, 2, CandidateSet,
+                          /*IsAssignmentOperator=*/false);
+
+      if (!Context.getCanonicalType(*Enum).isVolatileQualified()) {
+        // volatile T& operator=(volatile T&, T)
+        ParamTypes[0] = Context.getLValueReferenceType((*Enum).withVolatile());
+        ParamTypes[1] = *Enum;
+        AddBuiltinCandidate(ParamTypes[0], ParamTypes, Args, 2, CandidateSet,
+                            /*IsAssignmentOperator=*/false);
+      }
+    }
+    // Fall through.
+
+  case OO_PlusEqual:
+  case OO_MinusEqual:
+    // C++ [over.built]p19:
+    //
+    //   For every pair (T, VQ), where T is any type and VQ is either
+    //   volatile or empty, there exist candidate operator functions
+    //   of the form
+    //
+    //        T*VQ&      operator=(T*VQ&, T*);
+    //
+    // C++ [over.built]p21:
+    //
+    //   For every pair (T, VQ), where T is a cv-qualified or
+    //   cv-unqualified object type and VQ is either volatile or
+    //   empty, there exist candidate operator functions of the form
+    //
+    //        T*VQ&      operator+=(T*VQ&, ptrdiff_t);
+    //        T*VQ&      operator-=(T*VQ&, ptrdiff_t);
+    for (BuiltinCandidateTypeSet::iterator Ptr = CandidateTypes.pointer_begin();
+         Ptr != CandidateTypes.pointer_end(); ++Ptr) {
+      QualType ParamTypes[2];
+      ParamTypes[1] = (Op == OO_Equal)? *Ptr : Context.getPointerDiffType();
+
+      // non-volatile version
+      ParamTypes[0] = Context.getLValueReferenceType(*Ptr);
+      AddBuiltinCandidate(ParamTypes[0], ParamTypes, Args, 2, CandidateSet,
+                          /*IsAssigmentOperator=*/Op == OO_Equal);
+
+      if (!Context.getCanonicalType(*Ptr).isVolatileQualified()) {
+        // volatile version
+        ParamTypes[0] = Context.getLValueReferenceType((*Ptr).withVolatile());
+        AddBuiltinCandidate(ParamTypes[0], ParamTypes, Args, 2, CandidateSet,
+                            /*IsAssigmentOperator=*/Op == OO_Equal);
+      }
+    }
+    // Fall through.
+
+  case OO_StarEqual:
+  case OO_SlashEqual:
+    // C++ [over.built]p18:
+    //
+    //   For every triple (L, VQ, R), where L is an arithmetic type,
+    //   VQ is either volatile or empty, and R is a promoted
+    //   arithmetic type, there exist candidate operator functions of
+    //   the form
+    //
+    //        VQ L&      operator=(VQ L&, R);
+    //        VQ L&      operator*=(VQ L&, R);
+    //        VQ L&      operator/=(VQ L&, R);
+    //        VQ L&      operator+=(VQ L&, R);
+    //        VQ L&      operator-=(VQ L&, R);
+    for (unsigned Left = 0; Left < NumArithmeticTypes; ++Left) {
+      for (unsigned Right = FirstPromotedArithmeticType; 
+           Right < LastPromotedArithmeticType; ++Right) {
+        QualType ParamTypes[2];
+        ParamTypes[1] = ArithmeticTypes[Right];
+
+        // Add this built-in operator as a candidate (VQ is empty).
+        ParamTypes[0] = Context.getLValueReferenceType(ArithmeticTypes[Left]);
+        AddBuiltinCandidate(ParamTypes[0], ParamTypes, Args, 2, CandidateSet,
+                            /*IsAssigmentOperator=*/Op == OO_Equal);
+
+        // Add this built-in operator as a candidate (VQ is 'volatile').
+        ParamTypes[0] = ArithmeticTypes[Left].withVolatile();
+        ParamTypes[0] = Context.getLValueReferenceType(ParamTypes[0]);
+        AddBuiltinCandidate(ParamTypes[0], ParamTypes, Args, 2, CandidateSet,
+                            /*IsAssigmentOperator=*/Op == OO_Equal);
+      }
+    }
+    break;
+
+  case OO_PercentEqual:
+  case OO_LessLessEqual:
+  case OO_GreaterGreaterEqual:
+  case OO_AmpEqual:
+  case OO_CaretEqual:
+  case OO_PipeEqual:
+    // C++ [over.built]p22:
+    //
+    //   For every triple (L, VQ, R), where L is an integral type, VQ
+    //   is either volatile or empty, and R is a promoted integral
+    //   type, there exist candidate operator functions of the form
+    //
+    //        VQ L&       operator%=(VQ L&, R);
+    //        VQ L&       operator<<=(VQ L&, R);
+    //        VQ L&       operator>>=(VQ L&, R);
+    //        VQ L&       operator&=(VQ L&, R);
+    //        VQ L&       operator^=(VQ L&, R);
+    //        VQ L&       operator|=(VQ L&, R);
+    for (unsigned Left = FirstIntegralType; Left < LastIntegralType; ++Left) {
+      for (unsigned Right = FirstPromotedIntegralType; 
+           Right < LastPromotedIntegralType; ++Right) {
+        QualType ParamTypes[2];
+        ParamTypes[1] = ArithmeticTypes[Right];
+
+        // Add this built-in operator as a candidate (VQ is empty).
+        ParamTypes[0] = Context.getLValueReferenceType(ArithmeticTypes[Left]);
+        AddBuiltinCandidate(ParamTypes[0], ParamTypes, Args, 2, CandidateSet);
+
+        // Add this built-in operator as a candidate (VQ is 'volatile').
+        ParamTypes[0] = ArithmeticTypes[Left];
+        ParamTypes[0].addVolatile();
+        ParamTypes[0] = Context.getLValueReferenceType(ParamTypes[0]);
+        AddBuiltinCandidate(ParamTypes[0], ParamTypes, Args, 2, CandidateSet);
+      }
+    }
+    break;
+
+  case OO_Exclaim: {
+    // C++ [over.operator]p23:
+    //
+    //   There also exist candidate operator functions of the form
+    //
+    //        bool        operator!(bool);            
+    //        bool        operator&&(bool, bool);     [BELOW]
+    //        bool        operator||(bool, bool);     [BELOW]
+    QualType ParamTy = Context.BoolTy;
+    AddBuiltinCandidate(ParamTy, &ParamTy, Args, 1, CandidateSet,
+                        /*IsAssignmentOperator=*/false,
+                        /*NumContextualBoolArguments=*/1);
+    break;
+  }
+
+  case OO_AmpAmp:
+  case OO_PipePipe: {
+    // C++ [over.operator]p23:
+    //
+    //   There also exist candidate operator functions of the form
+    //
+    //        bool        operator!(bool);            [ABOVE]
+    //        bool        operator&&(bool, bool);
+    //        bool        operator||(bool, bool);
+    QualType ParamTypes[2] = { Context.BoolTy, Context.BoolTy };
+    AddBuiltinCandidate(Context.BoolTy, ParamTypes, Args, 2, CandidateSet,
+                        /*IsAssignmentOperator=*/false,
+                        /*NumContextualBoolArguments=*/2);
+    break;
+  }
+
+  case OO_Subscript:
+    // C++ [over.built]p13:
+    //
+    //   For every cv-qualified or cv-unqualified object type T there
+    //   exist candidate operator functions of the form
+    //    
+    //        T*         operator+(T*, ptrdiff_t);     [ABOVE]
+    //        T&         operator[](T*, ptrdiff_t);
+    //        T*         operator-(T*, ptrdiff_t);     [ABOVE]
+    //        T*         operator+(ptrdiff_t, T*);     [ABOVE]
+    //        T&         operator[](ptrdiff_t, T*);
+    for (BuiltinCandidateTypeSet::iterator Ptr = CandidateTypes.pointer_begin();
+         Ptr != CandidateTypes.pointer_end(); ++Ptr) {
+      QualType ParamTypes[2] = { *Ptr, Context.getPointerDiffType() };
+      QualType PointeeType = (*Ptr)->getAsPointerType()->getPointeeType();
+      QualType ResultTy = Context.getLValueReferenceType(PointeeType);
+
+      // T& operator[](T*, ptrdiff_t)
+      AddBuiltinCandidate(ResultTy, ParamTypes, Args, 2, CandidateSet);
+
+      // T& operator[](ptrdiff_t, T*);
+      ParamTypes[0] = ParamTypes[1];
+      ParamTypes[1] = *Ptr;
+      AddBuiltinCandidate(ResultTy, ParamTypes, Args, 2, CandidateSet);
+    }
+    break;
+
+  case OO_ArrowStar:
+    // FIXME: No support for pointer-to-members yet.
+    break;
+
+  case OO_Conditional:
+    // Note that we don't consider the first argument, since it has been
+    // contextually converted to bool long ago. The candidates below are
+    // therefore added as binary.
+    //
+    // C++ [over.built]p24:
+    //   For every type T, where T is a pointer or pointer-to-member type,
+    //   there exist candidate operator functions of the form
+    //
+    //        T        operator?(bool, T, T);
+    //
+    for (BuiltinCandidateTypeSet::iterator Ptr = CandidateTypes.pointer_begin(),
+         E = CandidateTypes.pointer_end(); Ptr != E; ++Ptr) {
+      QualType ParamTypes[2] = { *Ptr, *Ptr };
+      AddBuiltinCandidate(*Ptr, ParamTypes, Args, 2, CandidateSet);
+    }
+    for (BuiltinCandidateTypeSet::iterator Ptr =
+           CandidateTypes.member_pointer_begin(),
+         E = CandidateTypes.member_pointer_end(); Ptr != E; ++Ptr) {
+      QualType ParamTypes[2] = { *Ptr, *Ptr };
+      AddBuiltinCandidate(*Ptr, ParamTypes, Args, 2, CandidateSet);
+    }
+    goto Conditional;
+  }
+}
+
+/// \brief Add function candidates found via argument-dependent lookup
+/// to the set of overloading candidates.
+///
+/// This routine performs argument-dependent name lookup based on the
+/// given function name (which may also be an operator name) and adds
+/// all of the overload candidates found by ADL to the overload
+/// candidate set (C++ [basic.lookup.argdep]).
+void 
+Sema::AddArgumentDependentLookupCandidates(DeclarationName Name,
+                                           Expr **Args, unsigned NumArgs,
+                                           OverloadCandidateSet& CandidateSet) {
+  FunctionSet Functions;
+
+  // Record all of the function candidates that we've already
+  // added to the overload set, so that we don't add those same
+  // candidates a second time.
+  for (OverloadCandidateSet::iterator Cand = CandidateSet.begin(),
+                                   CandEnd = CandidateSet.end();
+       Cand != CandEnd; ++Cand)
+    if (Cand->Function)
+      Functions.insert(Cand->Function);
+
+  ArgumentDependentLookup(Name, Args, NumArgs, Functions);
+
+  // Erase all of the candidates we already knew about.
+  // FIXME: This is suboptimal. Is there a better way?
+  for (OverloadCandidateSet::iterator Cand = CandidateSet.begin(),
+                                   CandEnd = CandidateSet.end();
+       Cand != CandEnd; ++Cand)
+    if (Cand->Function)
+      Functions.erase(Cand->Function);
+
+  // For each of the ADL candidates we found, add it to the overload
+  // set.
+  for (FunctionSet::iterator Func = Functions.begin(),
+                          FuncEnd = Functions.end();
+       Func != FuncEnd; ++Func)
+    AddOverloadCandidate(*Func, Args, NumArgs, CandidateSet);
+}
+
+/// isBetterOverloadCandidate - Determines whether the first overload
+/// candidate is a better candidate than the second (C++ 13.3.3p1).
+bool 
+Sema::isBetterOverloadCandidate(const OverloadCandidate& Cand1,
+                                const OverloadCandidate& Cand2)
+{
+  // Define viable functions to be better candidates than non-viable
+  // functions.
+  if (!Cand2.Viable)
+    return Cand1.Viable;
+  else if (!Cand1.Viable)
+    return false;
+
+  // C++ [over.match.best]p1:
+  //
+  //   -- if F is a static member function, ICS1(F) is defined such
+  //      that ICS1(F) is neither better nor worse than ICS1(G) for
+  //      any function G, and, symmetrically, ICS1(G) is neither
+  //      better nor worse than ICS1(F).
+  unsigned StartArg = 0;
+  if (Cand1.IgnoreObjectArgument || Cand2.IgnoreObjectArgument)
+    StartArg = 1;
+
+  // (C++ 13.3.3p1): a viable function F1 is defined to be a better
+  // function than another viable function F2 if for all arguments i,
+  // ICSi(F1) is not a worse conversion sequence than ICSi(F2), and
+  // then...
+  unsigned NumArgs = Cand1.Conversions.size();
+  assert(Cand2.Conversions.size() == NumArgs && "Overload candidate mismatch");
+  bool HasBetterConversion = false;
+  for (unsigned ArgIdx = StartArg; ArgIdx < NumArgs; ++ArgIdx) {
+    switch (CompareImplicitConversionSequences(Cand1.Conversions[ArgIdx],
+                                               Cand2.Conversions[ArgIdx])) {
+    case ImplicitConversionSequence::Better:
+      // Cand1 has a better conversion sequence.
+      HasBetterConversion = true;
+      break;
+
+    case ImplicitConversionSequence::Worse:
+      // Cand1 can't be better than Cand2.
+      return false;
+
+    case ImplicitConversionSequence::Indistinguishable:
+      // Do nothing.
+      break;
+    }
+  }
+
+  if (HasBetterConversion)
+    return true;
+
+  // FIXME: Several other bullets in (C++ 13.3.3p1) need to be
+  // implemented, but they require template support.
+
+  // C++ [over.match.best]p1b4:
+  //
+  //   -- the context is an initialization by user-defined conversion
+  //      (see 8.5, 13.3.1.5) and the standard conversion sequence
+  //      from the return type of F1 to the destination type (i.e.,
+  //      the type of the entity being initialized) is a better
+  //      conversion sequence than the standard conversion sequence
+  //      from the return type of F2 to the destination type.
+  if (Cand1.Function && Cand2.Function && 
+      isa<CXXConversionDecl>(Cand1.Function) && 
+      isa<CXXConversionDecl>(Cand2.Function)) {
+    switch (CompareStandardConversionSequences(Cand1.FinalConversion,
+                                               Cand2.FinalConversion)) {
+    case ImplicitConversionSequence::Better:
+      // Cand1 has a better conversion sequence.
+      return true;
+
+    case ImplicitConversionSequence::Worse:
+      // Cand1 can't be better than Cand2.
+      return false;
+
+    case ImplicitConversionSequence::Indistinguishable:
+      // Do nothing
+      break;
+    }
+  }
+
+  return false;
+}
+
+/// BestViableFunction - Computes the best viable function (C++ 13.3.3) 
+/// within an overload candidate set. If overloading is successful,
+/// the result will be OR_Success and Best will be set to point to the
+/// best viable function within the candidate set. Otherwise, one of
+/// several kinds of errors will be returned; see
+/// Sema::OverloadingResult.
+Sema::OverloadingResult 
+Sema::BestViableFunction(OverloadCandidateSet& CandidateSet,
+                         OverloadCandidateSet::iterator& Best)
+{
+  // Find the best viable function.
+  Best = CandidateSet.end();
+  for (OverloadCandidateSet::iterator Cand = CandidateSet.begin();
+       Cand != CandidateSet.end(); ++Cand) {
+    if (Cand->Viable) {
+      if (Best == CandidateSet.end() || isBetterOverloadCandidate(*Cand, *Best))
+        Best = Cand;
+    }
+  }
+
+  // If we didn't find any viable functions, abort.
+  if (Best == CandidateSet.end())
+    return OR_No_Viable_Function;
+
+  // Make sure that this function is better than every other viable
+  // function. If not, we have an ambiguity.
+  for (OverloadCandidateSet::iterator Cand = CandidateSet.begin();
+       Cand != CandidateSet.end(); ++Cand) {
+    if (Cand->Viable && 
+        Cand != Best &&
+        !isBetterOverloadCandidate(*Best, *Cand)) {
+      Best = CandidateSet.end();
+      return OR_Ambiguous;
+    }
+  }
+  
+  // Best is the best viable function.
+  if (Best->Function &&
+      (Best->Function->isDeleted() || 
+       Best->Function->getAttr<UnavailableAttr>()))
+    return OR_Deleted;
+
+  // If Best refers to a function that is either deleted (C++0x) or
+  // unavailable (Clang extension) report an error.
+
+  return OR_Success;
+}
+
+/// PrintOverloadCandidates - When overload resolution fails, prints
+/// diagnostic messages containing the candidates in the candidate
+/// set. If OnlyViable is true, only viable candidates will be printed.
+void 
+Sema::PrintOverloadCandidates(OverloadCandidateSet& CandidateSet,
+                              bool OnlyViable)
+{
+  OverloadCandidateSet::iterator Cand = CandidateSet.begin(),
+                             LastCand = CandidateSet.end();
+  for (; Cand != LastCand; ++Cand) {
+    if (Cand->Viable || !OnlyViable) {
+      if (Cand->Function) {
+        if (Cand->Function->isDeleted() ||
+            Cand->Function->getAttr<UnavailableAttr>()) {
+          // Deleted or "unavailable" function.
+          Diag(Cand->Function->getLocation(), diag::err_ovl_candidate_deleted)
+            << Cand->Function->isDeleted();
+        } else {
+          // Normal function
+          // FIXME: Give a better reason!
+          Diag(Cand->Function->getLocation(), diag::err_ovl_candidate);
+        }
+      } else if (Cand->IsSurrogate) {
+        // Desugar the type of the surrogate down to a function type,
+        // retaining as many typedefs as possible while still showing
+        // the function type (and, therefore, its parameter types).
+        QualType FnType = Cand->Surrogate->getConversionType();
+        bool isLValueReference = false;
+        bool isRValueReference = false;
+        bool isPointer = false;
+        if (const LValueReferenceType *FnTypeRef =
+              FnType->getAsLValueReferenceType()) {
+          FnType = FnTypeRef->getPointeeType();
+          isLValueReference = true;
+        } else if (const RValueReferenceType *FnTypeRef =
+                     FnType->getAsRValueReferenceType()) {
+          FnType = FnTypeRef->getPointeeType();
+          isRValueReference = true;
+        }
+        if (const PointerType *FnTypePtr = FnType->getAsPointerType()) {
+          FnType = FnTypePtr->getPointeeType();
+          isPointer = true;
+        }
+        // Desugar down to a function type.
+        FnType = QualType(FnType->getAsFunctionType(), 0);
+        // Reconstruct the pointer/reference as appropriate.
+        if (isPointer) FnType = Context.getPointerType(FnType);
+        if (isRValueReference) FnType = Context.getRValueReferenceType(FnType);
+        if (isLValueReference) FnType = Context.getLValueReferenceType(FnType);
+
+        Diag(Cand->Surrogate->getLocation(), diag::err_ovl_surrogate_cand)
+          << FnType;
+      } else {
+        // FIXME: We need to get the identifier in here
+        // FIXME: Do we want the error message to point at the operator?
+        // (built-ins won't have a location)
+        QualType FnType 
+          = Context.getFunctionType(Cand->BuiltinTypes.ResultTy,
+                                    Cand->BuiltinTypes.ParamTypes,
+                                    Cand->Conversions.size(),
+                                    false, 0);
+
+        Diag(SourceLocation(), diag::err_ovl_builtin_candidate) << FnType;
+      }
+    }
+  }
+}
+
+/// ResolveAddressOfOverloadedFunction - Try to resolve the address of
+/// an overloaded function (C++ [over.over]), where @p From is an
+/// expression with overloaded function type and @p ToType is the type
+/// we're trying to resolve to. For example:
+///
+/// @code
+/// int f(double);
+/// int f(int);
+///                          
+/// int (*pfd)(double) = f; // selects f(double)
+/// @endcode
+///
+/// This routine returns the resulting FunctionDecl if it could be
+/// resolved, and NULL otherwise. When @p Complain is true, this
+/// routine will emit diagnostics if there is an error.
+FunctionDecl *
+Sema::ResolveAddressOfOverloadedFunction(Expr *From, QualType ToType,
+                                         bool Complain) {
+  QualType FunctionType = ToType;
+  bool IsMember = false;
+  if (const PointerType *ToTypePtr = ToType->getAsPointerType())
+    FunctionType = ToTypePtr->getPointeeType();
+  else if (const ReferenceType *ToTypeRef = ToType->getAsReferenceType())
+    FunctionType = ToTypeRef->getPointeeType();
+  else if (const MemberPointerType *MemTypePtr =
+                    ToType->getAsMemberPointerType()) {
+    FunctionType = MemTypePtr->getPointeeType();
+    IsMember = true;
+  }
+
+  // We only look at pointers or references to functions.
+  if (!FunctionType->isFunctionType()) 
+    return 0;
+
+  // Find the actual overloaded function declaration.
+  OverloadedFunctionDecl *Ovl = 0;
+  
+  // C++ [over.over]p1:
+  //   [...] [Note: any redundant set of parentheses surrounding the
+  //   overloaded function name is ignored (5.1). ]
+  Expr *OvlExpr = From->IgnoreParens();
+
+  // C++ [over.over]p1:
+  //   [...] The overloaded function name can be preceded by the &
+  //   operator.
+  if (UnaryOperator *UnOp = dyn_cast<UnaryOperator>(OvlExpr)) {
+    if (UnOp->getOpcode() == UnaryOperator::AddrOf)
+      OvlExpr = UnOp->getSubExpr()->IgnoreParens();
+  }
+
+  // Try to dig out the overloaded function.
+  if (DeclRefExpr *DR = dyn_cast<DeclRefExpr>(OvlExpr))
+    Ovl = dyn_cast<OverloadedFunctionDecl>(DR->getDecl());
+
+  // If there's no overloaded function declaration, we're done.
+  if (!Ovl)
+    return 0;
+ 
+  // Look through all of the overloaded functions, searching for one
+  // whose type matches exactly.
+  // FIXME: When templates or using declarations come along, we'll actually
+  // have to deal with duplicates, partial ordering, etc. For now, we 
+  // can just do a simple search.
+  FunctionType = Context.getCanonicalType(FunctionType.getUnqualifiedType());
+  for (OverloadedFunctionDecl::function_iterator Fun = Ovl->function_begin();
+       Fun != Ovl->function_end(); ++Fun) {
+    // C++ [over.over]p3:
+    //   Non-member functions and static member functions match
+    //   targets of type "pointer-to-function" or "reference-to-function."
+    //   Nonstatic member functions match targets of
+    //   type "pointer-to-member-function."
+    // Note that according to DR 247, the containing class does not matter.
+    if (CXXMethodDecl *Method = dyn_cast<CXXMethodDecl>(*Fun)) {
+      // Skip non-static functions when converting to pointer, and static
+      // when converting to member pointer.
+      if (Method->isStatic() == IsMember)
+        continue;
+    } else if (IsMember)
+      continue;
+
+    if (FunctionType == Context.getCanonicalType((*Fun)->getType()))
+      return *Fun;
+  }
+
+  return 0;
+}
+
+/// ResolveOverloadedCallFn - Given the call expression that calls Fn
+/// (which eventually refers to the declaration Func) and the call
+/// arguments Args/NumArgs, attempt to resolve the function call down
+/// to a specific function. If overload resolution succeeds, returns
+/// the function declaration produced by overload
+/// resolution. Otherwise, emits diagnostics, deletes all of the
+/// arguments and Fn, and returns NULL.
+FunctionDecl *Sema::ResolveOverloadedCallFn(Expr *Fn, NamedDecl *Callee,
+                                            DeclarationName UnqualifiedName,
+                                            SourceLocation LParenLoc,
+                                            Expr **Args, unsigned NumArgs,
+                                            SourceLocation *CommaLocs, 
+                                            SourceLocation RParenLoc,
+                                            bool &ArgumentDependentLookup) {
+  OverloadCandidateSet CandidateSet;
+
+  // Add the functions denoted by Callee to the set of candidate
+  // functions. While we're doing so, track whether argument-dependent
+  // lookup still applies, per:
+  //
+  // C++0x [basic.lookup.argdep]p3:
+  //   Let X be the lookup set produced by unqualified lookup (3.4.1)
+  //   and let Y be the lookup set produced by argument dependent
+  //   lookup (defined as follows). If X contains
+  //
+  //     -- a declaration of a class member, or 
+  //
+  //     -- a block-scope function declaration that is not a
+  //        using-declaration, or 
+  // 
+  //     -- a declaration that is neither a function or a function
+  //        template
+  //
+  //   then Y is empty. 
+  if (OverloadedFunctionDecl *Ovl 
+        = dyn_cast_or_null<OverloadedFunctionDecl>(Callee)) {
+    for (OverloadedFunctionDecl::function_iterator Func = Ovl->function_begin(),
+                                                FuncEnd = Ovl->function_end();
+         Func != FuncEnd; ++Func) {
+      AddOverloadCandidate(*Func, Args, NumArgs, CandidateSet);
+
+      if ((*Func)->getDeclContext()->isRecord() ||
+          (*Func)->getDeclContext()->isFunctionOrMethod())
+        ArgumentDependentLookup = false;
+    }
+  } else if (FunctionDecl *Func = dyn_cast_or_null<FunctionDecl>(Callee)) {
+    AddOverloadCandidate(Func, Args, NumArgs, CandidateSet);
+
+    if (Func->getDeclContext()->isRecord() ||
+        Func->getDeclContext()->isFunctionOrMethod())
+      ArgumentDependentLookup = false;
+  } 
+
+  if (Callee)
+    UnqualifiedName = Callee->getDeclName();
+
+  if (ArgumentDependentLookup)
+    AddArgumentDependentLookupCandidates(UnqualifiedName, Args, NumArgs,
+                                         CandidateSet);
+
+  OverloadCandidateSet::iterator Best;
+  switch (BestViableFunction(CandidateSet, Best)) {
+  case OR_Success:
+    return Best->Function;
+
+  case OR_No_Viable_Function:
+    Diag(Fn->getSourceRange().getBegin(),
+         diag::err_ovl_no_viable_function_in_call)
+      << UnqualifiedName << Fn->getSourceRange();
+    PrintOverloadCandidates(CandidateSet, /*OnlyViable=*/false);
+    break;
+
+  case OR_Ambiguous:
+    Diag(Fn->getSourceRange().getBegin(), diag::err_ovl_ambiguous_call)
+      << UnqualifiedName << Fn->getSourceRange();
+    PrintOverloadCandidates(CandidateSet, /*OnlyViable=*/true);
+    break;
+
+  case OR_Deleted:
+    Diag(Fn->getSourceRange().getBegin(), diag::err_ovl_deleted_call)
+      << Best->Function->isDeleted()
+      << UnqualifiedName
+      << Fn->getSourceRange();
+    PrintOverloadCandidates(CandidateSet, /*OnlyViable=*/true);
+    break;
+  }
+
+  // Overload resolution failed. Destroy all of the subexpressions and
+  // return NULL.
+  Fn->Destroy(Context);
+  for (unsigned Arg = 0; Arg < NumArgs; ++Arg)
+    Args[Arg]->Destroy(Context);
+  return 0;
+}
+
+/// \brief Create a unary operation that may resolve to an overloaded
+/// operator.
+///
+/// \param OpLoc The location of the operator itself (e.g., '*').
+///
+/// \param OpcIn The UnaryOperator::Opcode that describes this
+/// operator.
+///
+/// \param Functions The set of non-member functions that will be
+/// considered by overload resolution. The caller needs to build this
+/// set based on the context using, e.g.,
+/// LookupOverloadedOperatorName() and ArgumentDependentLookup(). This
+/// set should not contain any member functions; those will be added
+/// by CreateOverloadedUnaryOp().
+///
+/// \param input The input argument.
+Sema::OwningExprResult Sema::CreateOverloadedUnaryOp(SourceLocation OpLoc,
+                                                     unsigned OpcIn,
+                                                     FunctionSet &Functions,
+                                                     ExprArg input) {  
+  UnaryOperator::Opcode Opc = static_cast<UnaryOperator::Opcode>(OpcIn);
+  Expr *Input = (Expr *)input.get();
+
+  OverloadedOperatorKind Op = UnaryOperator::getOverloadedOperator(Opc);
+  assert(Op != OO_None && "Invalid opcode for overloaded unary operator");
+  DeclarationName OpName = Context.DeclarationNames.getCXXOperatorName(Op);
+
+  Expr *Args[2] = { Input, 0 };
+  unsigned NumArgs = 1;
+    
+  // For post-increment and post-decrement, add the implicit '0' as
+  // the second argument, so that we know this is a post-increment or
+  // post-decrement.
+  if (Opc == UnaryOperator::PostInc || Opc == UnaryOperator::PostDec) {
+    llvm::APSInt Zero(Context.getTypeSize(Context.IntTy), false);
+    Args[1] = new (Context) IntegerLiteral(Zero, Context.IntTy, 
+                                           SourceLocation());
+    NumArgs = 2;
+  }
+
+  if (Input->isTypeDependent()) {
+    OverloadedFunctionDecl *Overloads 
+      = OverloadedFunctionDecl::Create(Context, CurContext, OpName);
+    for (FunctionSet::iterator Func = Functions.begin(), 
+                            FuncEnd = Functions.end();
+         Func != FuncEnd; ++Func)
+      Overloads->addOverload(*Func);
+
+    DeclRefExpr *Fn = new (Context) DeclRefExpr(Overloads, Context.OverloadTy,
+                                                OpLoc, false, false);
+    
+    input.release();
+    return Owned(new (Context) CXXOperatorCallExpr(Context, Op, Fn,
+                                                   &Args[0], NumArgs,
+                                                   Context.DependentTy,
+                                                   OpLoc));
+  }
+
+  // Build an empty overload set.
+  OverloadCandidateSet CandidateSet;
+
+  // Add the candidates from the given function set.
+  AddFunctionCandidates(Functions, &Args[0], NumArgs, CandidateSet, false);
+
+  // Add operator candidates that are member functions.
+  AddMemberOperatorCandidates(Op, OpLoc, &Args[0], NumArgs, CandidateSet);
+
+  // Add builtin operator candidates.
+  AddBuiltinOperatorCandidates(Op, &Args[0], NumArgs, CandidateSet);
+
+  // Perform overload resolution.
+  OverloadCandidateSet::iterator Best;
+  switch (BestViableFunction(CandidateSet, Best)) {
+  case OR_Success: {
+    // We found a built-in operator or an overloaded operator.
+    FunctionDecl *FnDecl = Best->Function;
+    
+    if (FnDecl) {
+      // We matched an overloaded operator. Build a call to that
+      // operator.
+      
+      // Convert the arguments.
+      if (CXXMethodDecl *Method = dyn_cast<CXXMethodDecl>(FnDecl)) {
+        if (PerformObjectArgumentInitialization(Input, Method))
+          return ExprError();
+      } else {
+        // Convert the arguments.
+        if (PerformCopyInitialization(Input,
+                                      FnDecl->getParamDecl(0)->getType(),
+                                      "passing"))
+          return ExprError();
+      }
+
+      // Determine the result type
+      QualType ResultTy
+        = FnDecl->getType()->getAsFunctionType()->getResultType();
+      ResultTy = ResultTy.getNonReferenceType();
+      
+      // Build the actual expression node.
+      Expr *FnExpr = new (Context) DeclRefExpr(FnDecl, FnDecl->getType(),
+                                               SourceLocation());
+      UsualUnaryConversions(FnExpr);
+      
+      input.release();
+      return Owned(new (Context) CXXOperatorCallExpr(Context, Op, FnExpr,
+                                                     &Input, 1, ResultTy, 
+                                                     OpLoc));
+    } else {
+      // We matched a built-in operator. Convert the arguments, then
+      // break out so that we will build the appropriate built-in
+      // operator node.
+        if (PerformImplicitConversion(Input, Best->BuiltinTypes.ParamTypes[0],
+                                      Best->Conversions[0], "passing"))
+          return ExprError();
+
+        break;
+      }
+    }
+
+    case OR_No_Viable_Function:
+      // No viable function; fall through to handling this as a
+      // built-in operator, which will produce an error message for us.
+      break;
+
+    case OR_Ambiguous:
+      Diag(OpLoc,  diag::err_ovl_ambiguous_oper)
+          << UnaryOperator::getOpcodeStr(Opc)
+          << Input->getSourceRange();
+      PrintOverloadCandidates(CandidateSet, /*OnlyViable=*/true);
+      return ExprError();
+
+    case OR_Deleted:
+      Diag(OpLoc, diag::err_ovl_deleted_oper)
+        << Best->Function->isDeleted()
+        << UnaryOperator::getOpcodeStr(Opc)
+        << Input->getSourceRange();
+      PrintOverloadCandidates(CandidateSet, /*OnlyViable=*/true);
+      return ExprError();
+    }
+
+  // Either we found no viable overloaded operator or we matched a
+  // built-in operator. In either case, fall through to trying to
+  // build a built-in operation.
+  input.release();
+  return CreateBuiltinUnaryOp(OpLoc, Opc, Owned(Input));
+}
+
+/// \brief Create a binary operation that may resolve to an overloaded
+/// operator.
+///
+/// \param OpLoc The location of the operator itself (e.g., '+').
+///
+/// \param OpcIn The BinaryOperator::Opcode that describes this
+/// operator.
+///
+/// \param Functions The set of non-member functions that will be
+/// considered by overload resolution. The caller needs to build this
+/// set based on the context using, e.g.,
+/// LookupOverloadedOperatorName() and ArgumentDependentLookup(). This
+/// set should not contain any member functions; those will be added
+/// by CreateOverloadedBinOp().
+///
+/// \param LHS Left-hand argument.
+/// \param RHS Right-hand argument.
+Sema::OwningExprResult 
+Sema::CreateOverloadedBinOp(SourceLocation OpLoc,
+                            unsigned OpcIn, 
+                            FunctionSet &Functions,
+                            Expr *LHS, Expr *RHS) {
+  Expr *Args[2] = { LHS, RHS };
+
+  BinaryOperator::Opcode Opc = static_cast<BinaryOperator::Opcode>(OpcIn);
+  OverloadedOperatorKind Op = BinaryOperator::getOverloadedOperator(Opc);
+  DeclarationName OpName = Context.DeclarationNames.getCXXOperatorName(Op);
+
+  // If either side is type-dependent, create an appropriate dependent
+  // expression.
+  if (LHS->isTypeDependent() || RHS->isTypeDependent()) {
+    // .* cannot be overloaded.
+    if (Opc == BinaryOperator::PtrMemD)
+      return Owned(new (Context) BinaryOperator(LHS, RHS, Opc,
+                                                Context.DependentTy, OpLoc));
+
+    OverloadedFunctionDecl *Overloads 
+      = OverloadedFunctionDecl::Create(Context, CurContext, OpName);
+    for (FunctionSet::iterator Func = Functions.begin(), 
+                            FuncEnd = Functions.end();
+         Func != FuncEnd; ++Func)
+      Overloads->addOverload(*Func);
+
+    DeclRefExpr *Fn = new (Context) DeclRefExpr(Overloads, Context.OverloadTy,
+                                                OpLoc, false, false);
+    
+    return Owned(new (Context) CXXOperatorCallExpr(Context, Op, Fn,
+                                                   Args, 2, 
+                                                   Context.DependentTy,
+                                                   OpLoc));
+  }
+
+  // If this is the .* operator, which is not overloadable, just
+  // create a built-in binary operator.
+  if (Opc == BinaryOperator::PtrMemD)
+    return CreateBuiltinBinOp(OpLoc, Opc, LHS, RHS);
+
+  // If this is one of the assignment operators, we only perform
+  // overload resolution if the left-hand side is a class or
+  // enumeration type (C++ [expr.ass]p3).
+  if (Opc >= BinaryOperator::Assign && Opc <= BinaryOperator::OrAssign &&
+      !LHS->getType()->isOverloadableType())
+    return CreateBuiltinBinOp(OpLoc, Opc, LHS, RHS);
+
+  // Build an empty overload set.
+  OverloadCandidateSet CandidateSet;
+
+  // Add the candidates from the given function set.
+  AddFunctionCandidates(Functions, Args, 2, CandidateSet, false);
+
+  // Add operator candidates that are member functions.
+  AddMemberOperatorCandidates(Op, OpLoc, Args, 2, CandidateSet);
+
+  // Add builtin operator candidates.
+  AddBuiltinOperatorCandidates(Op, Args, 2, CandidateSet);
+
+  // Perform overload resolution.
+  OverloadCandidateSet::iterator Best;
+  switch (BestViableFunction(CandidateSet, Best)) {
+    case OR_Success: {
+      // We found a built-in operator or an overloaded operator.
+      FunctionDecl *FnDecl = Best->Function;
+
+      if (FnDecl) {
+        // We matched an overloaded operator. Build a call to that
+        // operator.
+
+        // Convert the arguments.
+        if (CXXMethodDecl *Method = dyn_cast<CXXMethodDecl>(FnDecl)) {
+          if (PerformObjectArgumentInitialization(LHS, Method) ||
+              PerformCopyInitialization(RHS, FnDecl->getParamDecl(0)->getType(),
+                                        "passing"))
+            return ExprError();
+        } else {
+          // Convert the arguments.
+          if (PerformCopyInitialization(LHS, FnDecl->getParamDecl(0)->getType(),
+                                        "passing") ||
+              PerformCopyInitialization(RHS, FnDecl->getParamDecl(1)->getType(),
+                                        "passing"))
+            return ExprError();
+        }
+
+        // Determine the result type
+        QualType ResultTy
+          = FnDecl->getType()->getAsFunctionType()->getResultType();
+        ResultTy = ResultTy.getNonReferenceType();
+
+        // Build the actual expression node.
+        Expr *FnExpr = new (Context) DeclRefExpr(FnDecl, FnDecl->getType(),
+                                                 SourceLocation());
+        UsualUnaryConversions(FnExpr);
+
+        return Owned(new (Context) CXXOperatorCallExpr(Context, Op, FnExpr, 
+                                                       Args, 2, ResultTy, 
+                                                       OpLoc));
+      } else {
+        // We matched a built-in operator. Convert the arguments, then
+        // break out so that we will build the appropriate built-in
+        // operator node.
+        if (PerformImplicitConversion(LHS, Best->BuiltinTypes.ParamTypes[0],
+                                      Best->Conversions[0], "passing") ||
+            PerformImplicitConversion(RHS, Best->BuiltinTypes.ParamTypes[1],
+                                      Best->Conversions[1], "passing"))
+          return ExprError();
+
+        break;
+      }
+    }
+
+    case OR_No_Viable_Function:
+      // For class as left operand for assignment or compound assigment operator
+      // do not fall through to handling in built-in, but report that no overloaded
+      // assignment operator found
+      if (LHS->getType()->isRecordType() && Opc >= BinaryOperator::Assign && Opc <= BinaryOperator::OrAssign) {
+        Diag(OpLoc,  diag::err_ovl_no_viable_oper)
+             << BinaryOperator::getOpcodeStr(Opc)
+             << LHS->getSourceRange() << RHS->getSourceRange();
+        return ExprError();
+      }
+      // No viable function; fall through to handling this as a
+      // built-in operator, which will produce an error message for us.
+      break;
+
+    case OR_Ambiguous:
+      Diag(OpLoc,  diag::err_ovl_ambiguous_oper)
+          << BinaryOperator::getOpcodeStr(Opc)
+          << LHS->getSourceRange() << RHS->getSourceRange();
+      PrintOverloadCandidates(CandidateSet, /*OnlyViable=*/true);
+      return ExprError();
+
+    case OR_Deleted:
+      Diag(OpLoc, diag::err_ovl_deleted_oper)
+        << Best->Function->isDeleted()
+        << BinaryOperator::getOpcodeStr(Opc)
+        << LHS->getSourceRange() << RHS->getSourceRange();
+      PrintOverloadCandidates(CandidateSet, /*OnlyViable=*/true);
+      return ExprError();
+    }
+
+  // Either we found no viable overloaded operator or we matched a
+  // built-in operator. In either case, try to build a built-in
+  // operation.
+  return CreateBuiltinBinOp(OpLoc, Opc, LHS, RHS);
+}
+
+/// BuildCallToMemberFunction - Build a call to a member
+/// function. MemExpr is the expression that refers to the member
+/// function (and includes the object parameter), Args/NumArgs are the
+/// arguments to the function call (not including the object
+/// parameter). The caller needs to validate that the member
+/// expression refers to a member function or an overloaded member
+/// function.
+Sema::ExprResult
+Sema::BuildCallToMemberFunction(Scope *S, Expr *MemExprE, 
+                                SourceLocation LParenLoc, Expr **Args, 
+                                unsigned NumArgs, SourceLocation *CommaLocs,
+                                SourceLocation RParenLoc) {
+  // Dig out the member expression. This holds both the object
+  // argument and the member function we're referring to.
+  MemberExpr *MemExpr = 0;
+  if (ParenExpr *ParenE = dyn_cast<ParenExpr>(MemExprE))
+    MemExpr = dyn_cast<MemberExpr>(ParenE->getSubExpr());
+  else
+    MemExpr = dyn_cast<MemberExpr>(MemExprE);
+  assert(MemExpr && "Building member call without member expression");
+
+  // Extract the object argument.
+  Expr *ObjectArg = MemExpr->getBase();
+
+  CXXMethodDecl *Method = 0;
+  if (OverloadedFunctionDecl *Ovl 
+        = dyn_cast<OverloadedFunctionDecl>(MemExpr->getMemberDecl())) {
+    // Add overload candidates
+    OverloadCandidateSet CandidateSet;
+    for (OverloadedFunctionDecl::function_iterator Func = Ovl->function_begin(),
+                                                FuncEnd = Ovl->function_end();
+         Func != FuncEnd; ++Func) {
+      assert(isa<CXXMethodDecl>(*Func) && "Function is not a method");
+      Method = cast<CXXMethodDecl>(*Func);
+      AddMethodCandidate(Method, ObjectArg, Args, NumArgs, CandidateSet, 
+                         /*SuppressUserConversions=*/false);
+    }
+
+    OverloadCandidateSet::iterator Best;
+    switch (BestViableFunction(CandidateSet, Best)) {
+    case OR_Success:
+      Method = cast<CXXMethodDecl>(Best->Function);
+      break;
+
+    case OR_No_Viable_Function:
+      Diag(MemExpr->getSourceRange().getBegin(), 
+           diag::err_ovl_no_viable_member_function_in_call)
+        << Ovl->getDeclName() << MemExprE->getSourceRange();
+      PrintOverloadCandidates(CandidateSet, /*OnlyViable=*/false);
+      // FIXME: Leaking incoming expressions!
+      return true;
+
+    case OR_Ambiguous:
+      Diag(MemExpr->getSourceRange().getBegin(), 
+           diag::err_ovl_ambiguous_member_call)
+        << Ovl->getDeclName() << MemExprE->getSourceRange();
+      PrintOverloadCandidates(CandidateSet, /*OnlyViable=*/false);
+      // FIXME: Leaking incoming expressions!
+      return true;
+
+    case OR_Deleted:
+      Diag(MemExpr->getSourceRange().getBegin(), 
+           diag::err_ovl_deleted_member_call)
+        << Best->Function->isDeleted()
+        << Ovl->getDeclName() << MemExprE->getSourceRange();
+      PrintOverloadCandidates(CandidateSet, /*OnlyViable=*/false);
+      // FIXME: Leaking incoming expressions!
+      return true;
+    }
+
+    FixOverloadedFunctionReference(MemExpr, Method);
+  } else {
+    Method = dyn_cast<CXXMethodDecl>(MemExpr->getMemberDecl());
+  }
+
+  assert(Method && "Member call to something that isn't a method?");
+  ExprOwningPtr<CXXMemberCallExpr> 
+    TheCall(this, new (Context) CXXMemberCallExpr(Context, MemExpr, Args,
+                                                  NumArgs, 
+                                  Method->getResultType().getNonReferenceType(),
+                                  RParenLoc));
+
+  // Convert the object argument (for a non-static member function call).
+  if (!Method->isStatic() && 
+      PerformObjectArgumentInitialization(ObjectArg, Method))
+    return true;
+  MemExpr->setBase(ObjectArg);
+
+  // Convert the rest of the arguments
+  const FunctionProtoType *Proto = cast<FunctionProtoType>(Method->getType());
+  if (ConvertArgumentsForCall(&*TheCall, MemExpr, Method, Proto, Args, NumArgs, 
+                              RParenLoc))
+    return true;
+
+  return CheckFunctionCall(Method, TheCall.take()).release();
+}
+
+/// BuildCallToObjectOfClassType - Build a call to an object of class
+/// type (C++ [over.call.object]), which can end up invoking an
+/// overloaded function call operator (@c operator()) or performing a
+/// user-defined conversion on the object argument.
+Sema::ExprResult 
+Sema::BuildCallToObjectOfClassType(Scope *S, Expr *Object, 
+                                   SourceLocation LParenLoc,
+                                   Expr **Args, unsigned NumArgs,
+                                   SourceLocation *CommaLocs, 
+                                   SourceLocation RParenLoc) {
+  assert(Object->getType()->isRecordType() && "Requires object type argument");
+  const RecordType *Record = Object->getType()->getAsRecordType();
+  
+  // C++ [over.call.object]p1:
+  //  If the primary-expression E in the function call syntax
+  //  evaluates to a class object of type “cv T”, then the set of
+  //  candidate functions includes at least the function call
+  //  operators of T. The function call operators of T are obtained by
+  //  ordinary lookup of the name operator() in the context of
+  //  (E).operator().
+  OverloadCandidateSet CandidateSet;
+  DeclarationName OpName = Context.DeclarationNames.getCXXOperatorName(OO_Call);
+  DeclContext::lookup_const_iterator Oper, OperEnd;
+  for (llvm::tie(Oper, OperEnd) = Record->getDecl()->lookup(Context, OpName);
+       Oper != OperEnd; ++Oper)
+    AddMethodCandidate(cast<CXXMethodDecl>(*Oper), Object, Args, NumArgs, 
+                       CandidateSet, /*SuppressUserConversions=*/false);
+
+  // C++ [over.call.object]p2:
+  //   In addition, for each conversion function declared in T of the
+  //   form
+  //
+  //        operator conversion-type-id () cv-qualifier;
+  //
+  //   where cv-qualifier is the same cv-qualification as, or a
+  //   greater cv-qualification than, cv, and where conversion-type-id
+  //   denotes the type "pointer to function of (P1,...,Pn) returning
+  //   R", or the type "reference to pointer to function of
+  //   (P1,...,Pn) returning R", or the type "reference to function
+  //   of (P1,...,Pn) returning R", a surrogate call function [...]
+  //   is also considered as a candidate function. Similarly,
+  //   surrogate call functions are added to the set of candidate
+  //   functions for each conversion function declared in an
+  //   accessible base class provided the function is not hidden
+  //   within T by another intervening declaration.
+  //
+  // FIXME: Look in base classes for more conversion operators!
+  OverloadedFunctionDecl *Conversions 
+    = cast<CXXRecordDecl>(Record->getDecl())->getConversionFunctions();
+  for (OverloadedFunctionDecl::function_iterator 
+         Func = Conversions->function_begin(),
+         FuncEnd = Conversions->function_end();
+       Func != FuncEnd; ++Func) {
+    CXXConversionDecl *Conv = cast<CXXConversionDecl>(*Func);
+
+    // Strip the reference type (if any) and then the pointer type (if
+    // any) to get down to what might be a function type.
+    QualType ConvType = Conv->getConversionType().getNonReferenceType();
+    if (const PointerType *ConvPtrType = ConvType->getAsPointerType())
+      ConvType = ConvPtrType->getPointeeType();
+
+    if (const FunctionProtoType *Proto = ConvType->getAsFunctionProtoType())
+      AddSurrogateCandidate(Conv, Proto, Object, Args, NumArgs, CandidateSet);
+  }
+
+  // Perform overload resolution.
+  OverloadCandidateSet::iterator Best;
+  switch (BestViableFunction(CandidateSet, Best)) {
+  case OR_Success:
+    // Overload resolution succeeded; we'll build the appropriate call
+    // below.
+    break;
+
+  case OR_No_Viable_Function:
+    Diag(Object->getSourceRange().getBegin(), 
+         diag::err_ovl_no_viable_object_call)
+      << Object->getType() << Object->getSourceRange();
+    PrintOverloadCandidates(CandidateSet, /*OnlyViable=*/false);
+    break;
+
+  case OR_Ambiguous:
+    Diag(Object->getSourceRange().getBegin(),
+         diag::err_ovl_ambiguous_object_call)
+      << Object->getType() << Object->getSourceRange();
+    PrintOverloadCandidates(CandidateSet, /*OnlyViable=*/true);
+    break;
+
+  case OR_Deleted:
+    Diag(Object->getSourceRange().getBegin(),
+         diag::err_ovl_deleted_object_call)
+      << Best->Function->isDeleted()
+      << Object->getType() << Object->getSourceRange();
+    PrintOverloadCandidates(CandidateSet, /*OnlyViable=*/true);
+    break;
+  }    
+
+  if (Best == CandidateSet.end()) {
+    // We had an error; delete all of the subexpressions and return
+    // the error.
+    Object->Destroy(Context);
+    for (unsigned ArgIdx = 0; ArgIdx < NumArgs; ++ArgIdx)
+      Args[ArgIdx]->Destroy(Context);
+    return true;
+  }
+
+  if (Best->Function == 0) {
+    // Since there is no function declaration, this is one of the
+    // surrogate candidates. Dig out the conversion function.
+    CXXConversionDecl *Conv 
+      = cast<CXXConversionDecl>(
+                         Best->Conversions[0].UserDefined.ConversionFunction);
+
+    // We selected one of the surrogate functions that converts the
+    // object parameter to a function pointer. Perform the conversion
+    // on the object argument, then let ActOnCallExpr finish the job.
+    // FIXME: Represent the user-defined conversion in the AST!
+    ImpCastExprToType(Object,
+                      Conv->getConversionType().getNonReferenceType(),
+                      Conv->getConversionType()->isLValueReferenceType());
+    return ActOnCallExpr(S, ExprArg(*this, Object), LParenLoc,
+                         MultiExprArg(*this, (ExprTy**)Args, NumArgs),
+                         CommaLocs, RParenLoc).release();
+  }
+
+  // We found an overloaded operator(). Build a CXXOperatorCallExpr
+  // that calls this method, using Object for the implicit object
+  // parameter and passing along the remaining arguments.
+  CXXMethodDecl *Method = cast<CXXMethodDecl>(Best->Function);
+  const FunctionProtoType *Proto = Method->getType()->getAsFunctionProtoType();
+
+  unsigned NumArgsInProto = Proto->getNumArgs();
+  unsigned NumArgsToCheck = NumArgs;
+
+  // Build the full argument list for the method call (the
+  // implicit object parameter is placed at the beginning of the
+  // list).
+  Expr **MethodArgs;
+  if (NumArgs < NumArgsInProto) {
+    NumArgsToCheck = NumArgsInProto;
+    MethodArgs = new Expr*[NumArgsInProto + 1];
+  } else {
+    MethodArgs = new Expr*[NumArgs + 1];
+  }
+  MethodArgs[0] = Object;
+  for (unsigned ArgIdx = 0; ArgIdx < NumArgs; ++ArgIdx)
+    MethodArgs[ArgIdx + 1] = Args[ArgIdx];
+      
+  Expr *NewFn = new (Context) DeclRefExpr(Method, Method->getType(), 
+                                          SourceLocation());
+  UsualUnaryConversions(NewFn);
+
+  // Once we've built TheCall, all of the expressions are properly
+  // owned.
+  QualType ResultTy = Method->getResultType().getNonReferenceType();
+  ExprOwningPtr<CXXOperatorCallExpr> 
+    TheCall(this, new (Context) CXXOperatorCallExpr(Context, OO_Call, NewFn, 
+                                                    MethodArgs, NumArgs + 1,
+                                                    ResultTy, RParenLoc));
+  delete [] MethodArgs;
+
+  // We may have default arguments. If so, we need to allocate more
+  // slots in the call for them.
+  if (NumArgs < NumArgsInProto)
+    TheCall->setNumArgs(Context, NumArgsInProto + 1);
+  else if (NumArgs > NumArgsInProto)
+    NumArgsToCheck = NumArgsInProto;
+
+  bool IsError = false;
+
+  // Initialize the implicit object parameter.
+  IsError |= PerformObjectArgumentInitialization(Object, Method);
+  TheCall->setArg(0, Object);
+
+
+  // Check the argument types.
+  for (unsigned i = 0; i != NumArgsToCheck; i++) {
+    Expr *Arg;
+    if (i < NumArgs) {
+      Arg = Args[i];
+      
+      // Pass the argument.
+      QualType ProtoArgType = Proto->getArgType(i);
+      IsError |= PerformCopyInitialization(Arg, ProtoArgType, "passing");
+    } else {
+      Arg = new (Context) CXXDefaultArgExpr(Method->getParamDecl(i));
+    }
+
+    TheCall->setArg(i + 1, Arg);
+  }
+
+  // If this is a variadic call, handle args passed through "...".
+  if (Proto->isVariadic()) {
+    // Promote the arguments (C99 6.5.2.2p7).
+    for (unsigned i = NumArgsInProto; i != NumArgs; i++) {
+      Expr *Arg = Args[i];
+      IsError |= DefaultVariadicArgumentPromotion(Arg, VariadicMethod);
+      TheCall->setArg(i + 1, Arg);
+    }
+  }
+
+  if (IsError) return true;
+
+  return CheckFunctionCall(Method, TheCall.take()).release();
+}
+
+/// BuildOverloadedArrowExpr - Build a call to an overloaded @c operator->
+///  (if one exists), where @c Base is an expression of class type and 
+/// @c Member is the name of the member we're trying to find.
+Action::ExprResult 
+Sema::BuildOverloadedArrowExpr(Scope *S, Expr *Base, SourceLocation OpLoc,
+                               SourceLocation MemberLoc,
+                               IdentifierInfo &Member) {
+  assert(Base->getType()->isRecordType() && "left-hand side must have class type");
+  
+  // C++ [over.ref]p1:
+  //
+  //   [...] An expression x->m is interpreted as (x.operator->())->m
+  //   for a class object x of type T if T::operator->() exists and if
+  //   the operator is selected as the best match function by the
+  //   overload resolution mechanism (13.3).
+  // FIXME: look in base classes.
+  DeclarationName OpName = Context.DeclarationNames.getCXXOperatorName(OO_Arrow);
+  OverloadCandidateSet CandidateSet;
+  const RecordType *BaseRecord = Base->getType()->getAsRecordType();
+  
+  DeclContext::lookup_const_iterator Oper, OperEnd;
+  for (llvm::tie(Oper, OperEnd) 
+         = BaseRecord->getDecl()->lookup(Context, OpName);
+       Oper != OperEnd; ++Oper)
+    AddMethodCandidate(cast<CXXMethodDecl>(*Oper), Base, 0, 0, CandidateSet,
+                       /*SuppressUserConversions=*/false);
+
+  ExprOwningPtr<Expr> BasePtr(this, Base);
+
+  // Perform overload resolution.
+  OverloadCandidateSet::iterator Best;
+  switch (BestViableFunction(CandidateSet, Best)) {
+  case OR_Success:
+    // Overload resolution succeeded; we'll build the call below.
+    break;
+
+  case OR_No_Viable_Function:
+    if (CandidateSet.empty())
+      Diag(OpLoc, diag::err_typecheck_member_reference_arrow)
+        << BasePtr->getType() << BasePtr->getSourceRange();
+    else
+      Diag(OpLoc, diag::err_ovl_no_viable_oper)
+        << "operator->" << BasePtr->getSourceRange();
+    PrintOverloadCandidates(CandidateSet, /*OnlyViable=*/false);
+    return true;
+
+  case OR_Ambiguous:
+    Diag(OpLoc,  diag::err_ovl_ambiguous_oper)
+      << "operator->" << BasePtr->getSourceRange();
+    PrintOverloadCandidates(CandidateSet, /*OnlyViable=*/true);
+    return true;
+
+  case OR_Deleted:
+    Diag(OpLoc,  diag::err_ovl_deleted_oper)
+      << Best->Function->isDeleted()
+      << "operator->" << BasePtr->getSourceRange();
+    PrintOverloadCandidates(CandidateSet, /*OnlyViable=*/true);
+    return true;
+  }
+
+  // Convert the object parameter.
+  CXXMethodDecl *Method = cast<CXXMethodDecl>(Best->Function);
+  if (PerformObjectArgumentInitialization(Base, Method))
+    return true;
+
+  // No concerns about early exits now.
+  BasePtr.take();
+
+  // Build the operator call.
+  Expr *FnExpr = new (Context) DeclRefExpr(Method, Method->getType(),
+                                           SourceLocation());
+  UsualUnaryConversions(FnExpr);
+  Base = new (Context) CXXOperatorCallExpr(Context, OO_Arrow, FnExpr, &Base, 1, 
+                                 Method->getResultType().getNonReferenceType(),
+                                 OpLoc);
+  return ActOnMemberReferenceExpr(S, ExprArg(*this, Base), OpLoc, tok::arrow,
+                                  MemberLoc, Member, DeclPtrTy()).release();
+}
+
+/// FixOverloadedFunctionReference - E is an expression that refers to
+/// a C++ overloaded function (possibly with some parentheses and
+/// perhaps a '&' around it). We have resolved the overloaded function
+/// to the function declaration Fn, so patch up the expression E to
+/// refer (possibly indirectly) to Fn.
+void Sema::FixOverloadedFunctionReference(Expr *E, FunctionDecl *Fn) {
+  if (ParenExpr *PE = dyn_cast<ParenExpr>(E)) {
+    FixOverloadedFunctionReference(PE->getSubExpr(), Fn);
+    E->setType(PE->getSubExpr()->getType());
+  } else if (UnaryOperator *UnOp = dyn_cast<UnaryOperator>(E)) {
+    assert(UnOp->getOpcode() == UnaryOperator::AddrOf && 
+           "Can only take the address of an overloaded function");
+    if (CXXMethodDecl *Method = dyn_cast<CXXMethodDecl>(Fn)) {
+      if (Method->isStatic()) {
+        // Do nothing: static member functions aren't any different
+        // from non-member functions.
+      }
+      else if (QualifiedDeclRefExpr *DRE 
+                 = dyn_cast<QualifiedDeclRefExpr>(UnOp->getSubExpr())) {
+        // We have taken the address of a pointer to member
+        // function. Perform the computation here so that we get the
+        // appropriate pointer to member type.
+        DRE->setDecl(Fn);
+        DRE->setType(Fn->getType());
+        QualType ClassType
+          = Context.getTypeDeclType(cast<RecordDecl>(Method->getDeclContext()));
+        E->setType(Context.getMemberPointerType(Fn->getType(), 
+                                                ClassType.getTypePtr()));
+        return;
+      }
+    }
+    FixOverloadedFunctionReference(UnOp->getSubExpr(), Fn);
+    E->setType(Context.getPointerType(UnOp->getSubExpr()->getType()));
+  } else if (DeclRefExpr *DR = dyn_cast<DeclRefExpr>(E)) {
+    assert(isa<OverloadedFunctionDecl>(DR->getDecl()) && 
+           "Expected overloaded function");
+    DR->setDecl(Fn);
+    E->setType(Fn->getType());
+  } else if (MemberExpr *MemExpr = dyn_cast<MemberExpr>(E)) {
+    MemExpr->setMemberDecl(Fn);
+    E->setType(Fn->getType());
+  } else {
+    assert(false && "Invalid reference to overloaded function");
+  }
+}
+
+} // end namespace clang